Async Wheel Event with only the first one cancellable behind a flag.

content/browser/renderer_host/render_widget_host_view_aura_unittest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/renderer_host/render_widget_host_view_aura.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <tuple>
@@ skipping 557 matching lines @@
 
 const WebInputEvent* GetInputEventFromMessage(const IPC::Message& message) {
   base::PickleIterator iter(message);
   const char* data;
   int data_length;
   if (!iter.ReadData(&data, &data_length))
     return nullptr;
   return reinterpret_cast<const WebInputEvent*>(data);
 }
 
+enum WheelScrollingMode {
+  kWheelScrollingModeNone,
+  kWheelScrollLatching,
+  kAsyncWheelEvents,
+};
+
 }  // namespace
 
 class RenderWidgetHostViewAuraTest : public testing::Test {
  public:
   RenderWidgetHostViewAuraTest()
       : widget_host_uses_shutdown_to_destroy_(false),
         is_guest_view_hack_(false) {}
 
   static void InstallDelegatedFrameHostClient(
       RenderWidgetHostViewAura* render_widget_host_view,
@@ skipping 147 matching lines @@
   void EnableWheelScrollLatching() {
     feature_list_.InitFromCommandLine(
         features::kTouchpadAndWheelScrollLatching.name, "");
   }
 
   void DisableWheelScrollLatching() {
     feature_list_.InitFromCommandLine(
         "", features::kTouchpadAndWheelScrollLatching.name);
   }
 
-  void SetFeatureList(bool raf_aligned_touch, bool wheel_scroll_latching) {
-    if (raf_aligned_touch && wheel_scroll_latching) {
+  void SetFeatureList(
+      bool raf_aligned_touch,
+      WheelScrollingMode wheel_scrolling_mode = kWheelScrollLatching) {
+    if (raf_aligned_touch && wheel_scrolling_mode == kAsyncWheelEvents) {
+      feature_list_.InitWithFeatures({features::kRafAlignedTouchInputEvents,
+                                      features::kTouchpadAndWheelScrollLatching,
+                                      features::kAsyncWheelEvents},
+                                     {});
+    } else if (raf_aligned_touch &&
+               wheel_scrolling_mode == kWheelScrollLatching) {
       feature_list_.InitWithFeatures(
           {features::kRafAlignedTouchInputEvents,
            features::kTouchpadAndWheelScrollLatching},
-          {});
-    } else if (raf_aligned_touch && !wheel_scroll_latching) {
-      feature_list_.InitWithFeatures(
-          {features::kRafAlignedTouchInputEvents},
-          {features::kTouchpadAndWheelScrollLatching});
-    } else if (!raf_aligned_touch && wheel_scroll_latching) {
+          {features::kAsyncWheelEvents});
+    } else if (raf_aligned_touch &&
+               wheel_scrolling_mode == kWheelScrollingModeNone) {
+      feature_list_.InitWithFeatures({features::kRafAlignedTouchInputEvents},
+                                     {features::kTouchpadAndWheelScrollLatching,
+                                      features::kAsyncWheelEvents});
+    } else if (!raf_aligned_touch &&
+               wheel_scrolling_mode == kAsyncWheelEvents) {
+      feature_list_.InitWithFeatures({features::kTouchpadAndWheelScrollLatching,
+                                      features::kAsyncWheelEvents},
+                                     {features::kRafAlignedTouchInputEvents});
+    } else if (!raf_aligned_touch &&
+               wheel_scrolling_mode == kWheelScrollLatching) {
       feature_list_.InitWithFeatures(
           {features::kTouchpadAndWheelScrollLatching},
-          {features::kRafAlignedTouchInputEvents});
-    } else {  // !raf_aligned_touch && !wheel_scroll_latching
-      feature_list_.InitWithFeatures(
-          {}, {features::kRafAlignedTouchInputEvents,
-               features::kTouchpadAndWheelScrollLatching});
+          {features::kRafAlignedTouchInputEvents, features::kAsyncWheelEvents});
+    } else {  // !raf_aligned_touch && wheel_scroll_latching ==
+              // kWheelScrollingModeNone.
+      feature_list_.InitWithFeatures({},
+                                     {features::kRafAlignedTouchInputEvents,
+                                      features::kTouchpadAndWheelScrollLatching,
+                                      features::kAsyncWheelEvents});
     }
   }
 
  protected:
   BrowserContext* browser_context() { return browser_context_.get(); }
 
   MockRenderWidgetHostDelegate* render_widget_host_delegate() const {
     return delegates_.back().get();
   }
 
@@ skipping 125 matching lines @@
 
  private:
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostViewGuestAuraTest);
 };
 
 class RenderWidgetHostViewAuraOverscrollTest
     : public RenderWidgetHostViewAuraTest {
  public:
   RenderWidgetHostViewAuraOverscrollTest(
-      bool wheel_scroll_latching_enabled = true)
-      : wheel_scroll_latching_enabled_(wheel_scroll_latching_enabled) {}
+      WheelScrollingMode wheel_scrolling_mode = kWheelScrollLatching)
+      : wheel_scroll_latching_enabled_(wheel_scrolling_mode !=
+                                       kWheelScrollingModeNone),
+        wheel_scrolling_mode_(wheel_scrolling_mode) {}
 
   // We explicitly invoke SetUp to allow gesture debounce customization.
   void SetUp() override {}
 
  protected:
   void SetUpOverscrollEnvironmentWithDebounce(int debounce_interval_in_ms) {
     SetUpOverscrollEnvironmentImpl(debounce_interval_in_ms);
   }
 
   void SetUpOverscrollEnvironment() { SetUpOverscrollEnvironmentImpl(0); }
 
   void SetUpOverscrollEnvironmentImpl(int debounce_interval_in_ms) {
-    SetFeatureList(true, wheel_scroll_latching_enabled_);
+    SetFeatureList(true, wheel_scrolling_mode_);
     ui::GestureConfiguration::GetInstance()->set_scroll_debounce_interval_in_ms(
         debounce_interval_in_ms);
 
     RenderWidgetHostViewAuraTest::SetUp();
 
     view_->SetOverscrollControllerEnabled(true);
     overscroll_delegate_.reset(new TestOverscrollDelegate(view_));
     view_->overscroll_controller()->set_delegate(overscroll_delegate_.get());
 
     view_->InitAsChild(nullptr);
@@ skipping 185 matching lines @@
 
     EXPECT_EQ(1U, sink_->message_count());
     InputMsg_HandleInputEvent::Param params;
     if (InputMsg_HandleInputEvent::Read(sink_->GetMessageAt(0), &params)) {
       const blink::WebInputEvent* event = std::get<0>(params);
       EXPECT_EQ(WebInputEvent::kGestureScrollEnd, event->GetType());
     }
     EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
   }
 
-  void ExpectGestureScrollEventsAfterMouseWheelACK(bool is_first_ack,
-                                                   bool enqueued_mouse_wheel) {
+  void ExpectGestureScrollEventsAfterMouseWheelACK(
+      bool is_first_ack,
+      size_t enqueued_wheel_event_count) {
     InputMsg_HandleInputEvent::Param params;
     const blink::WebInputEvent* event;
     size_t expected_message_count;
     if (is_first_ack) {
-      expected_message_count = enqueued_mouse_wheel ? 3 : 2;
+      if (wheel_scrolling_mode_ == kAsyncWheelEvents) {
+        // If the ack for the first sent event is not consumed,
+        // MouseWheelEventQueue(MWEQ) sends the rest of the wheel events in the
+        // current scrolling sequence as non-blocking events. Since MWEQ
+        // receives the ack for non-blocking events asynchronously, it sends the
+        // next queued wheel event immediately and this continues till the queue
+        // is empty.
+        expected_message_count = enqueued_wheel_event_count + 2;
+      } else {
+        // Since the MWEQ must wait for ack of the sent event before sending the
+        // next queued event, when wheel events are blocking only one queued
+        // event will be sent regardless of the number of the queued wheel
+        // events.
+        expected_message_count = enqueued_wheel_event_count ? 3 : 2;
+      }
+
       EXPECT_EQ(expected_message_count, sink_->message_count());
 
       // The first message is GestureScrollBegin.
       if (InputMsg_HandleInputEvent::Read(sink_->GetMessageAt(0), &params)) {
         event = std::get<0>(params);
         EXPECT_EQ(WebInputEvent::kGestureScrollBegin, event->GetType());
       }
 
       // The second message is GestureScrollUpdate.
       if (InputMsg_HandleInputEvent::Read(sink_->GetMessageAt(1), &params)) {
         event = std::get<0>(params);
         EXPECT_EQ(WebInputEvent::kGestureScrollUpdate, event->GetType());
       }
 
-      if (enqueued_mouse_wheel) {
-        // The last message is the queued MouseWheel.
-        if (InputMsg_HandleInputEvent::Read(sink_->GetMessageAt(2), &params)) {
+      for (size_t i = 2; i < expected_message_count; i++) {
+        // The last messages are the queued MouseWheel event(s).
+        if (InputMsg_HandleInputEvent::Read(sink_->GetMessageAt(i), &params)) {
           event = std::get<0>(params);
           EXPECT_EQ(WebInputEvent::kMouseWheel, event->GetType());
         }
       }
     } else {  // !is_first_ack
-      expected_message_count = enqueued_mouse_wheel ? 2 : 1;
+      expected_message_count = enqueued_wheel_event_count ? 2 : 1;
       size_t scroll_update_index = 0;
 
       if (!wheel_scroll_latching_enabled_) {
         // The first message is GestureScrollBegin even in the middle of
         // scrolling.
         if (InputMsg_HandleInputEvent::Read(sink_->GetMessageAt(0), &params)) {
           event = std::get<0>(params);
           EXPECT_EQ(WebInputEvent::kGestureScrollBegin, event->GetType());
         }
         expected_message_count++;
         scroll_update_index++;
       }
 
       // Check the GestureScrollUpdate message.
       if (InputMsg_HandleInputEvent::Read(
               sink_->GetMessageAt(scroll_update_index), &params)) {
         event = std::get<0>(params);
         EXPECT_EQ(WebInputEvent::kGestureScrollUpdate, event->GetType());
       }
 
-      if (enqueued_mouse_wheel) {
+      if (enqueued_wheel_event_count) {
         // The last message is the queued MouseWheel.
         if (InputMsg_HandleInputEvent::Read(
                 sink_->GetMessageAt(expected_message_count - 1), &params)) {
           event = std::get<0>(params);
           EXPECT_EQ(WebInputEvent::kMouseWheel, event->GetType());
         }
       }
     }
     EXPECT_EQ(expected_message_count, GetSentMessageCountAndResetSink());
   }
 
+  void ExpectGestureScrollUpdateAfterNonBlockingMouseWheelACK(
+      bool wheel_was_queued) {
+    size_t gesture_scroll_update_index;
+    InputMsg_HandleInputEvent::Param params;
+    if (wheel_was_queued) {
+      // The queued wheel event is already sent.
+      gesture_scroll_update_index = 0;
+    } else {
+      // The first sent must be the wheel event and the second one must be
+      // GestureScrollUpdate since the ack for the wheel event is non-blocking.
+      if (InputMsg_HandleInputEvent::Read(sink_->GetMessageAt(0), &params)) {
+        EXPECT_EQ(WebInputEvent::kMouseWheel, (std::get<0>(params))->GetType());
+      }
+      gesture_scroll_update_index = 1;
+    }
+    if (InputMsg_HandleInputEvent::Read(
+            sink_->GetMessageAt(gesture_scroll_update_index), &params)) {
+      EXPECT_EQ(WebInputEvent::kGestureScrollUpdate,
+                (std::get<0>(params))->GetType());
+    }
+    EXPECT_EQ(gesture_scroll_update_index + 1,
+              GetSentMessageCountAndResetSink());
+  }
+
+  void ExpectGestureScrollEndAfterNonBlockingMouseWheelACK() {
+    InputMsg_HandleInputEvent::Param params;
+    // The first sent must be the wheel event and the second one must be
+    // GestureScrollEnd since the ack for the wheel event is non-blocking.
+    if (InputMsg_HandleInputEvent::Read(sink_->GetMessageAt(0), &params)) {
+      EXPECT_EQ(WebInputEvent::kMouseWheel, (std::get<0>(params))->GetType());
+    }
+
+    if (InputMsg_HandleInputEvent::Read(sink_->GetMessageAt(1), &params)) {
+      EXPECT_EQ(WebInputEvent::kGestureScrollEnd,
+                (std::get<0>(params))->GetType());
+    }
+    EXPECT_EQ(2U, GetSentMessageCountAndResetSink());
+  }
+
   void WheelNotPreciseScrollEvent();
   void WheelScrollOverscrollToggle();
   void OverscrollMouseMoveCompletion();
   void WheelScrollEventOverscrolls();
   void WheelScrollConsumedDoNotHorizOverscroll();
   void ScrollEventsOverscrollWithFling();
   void OverscrollDirectionChangeMouseWheel();
   void OverscrollStateResetsAfterScroll();
+  void ScrollDeltasResetOnEnd();
   void ScrollEventsOverscrollWithZeroFling();
 
   SyntheticWebTouchEvent touch_event_;
 
   std::unique_ptr<TestOverscrollDelegate> overscroll_delegate_;
 
   bool wheel_scroll_latching_enabled_;
+  WheelScrollingMode wheel_scrolling_mode_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostViewAuraOverscrollTest);
 };
 
 class RenderWidgetHostViewAuraOverscrollWithoutWheelScrollLatchingTest
     : public RenderWidgetHostViewAuraOverscrollTest {
  public:
   RenderWidgetHostViewAuraOverscrollWithoutWheelScrollLatchingTest()
-      : RenderWidgetHostViewAuraOverscrollTest(false) {}
+      : RenderWidgetHostViewAuraOverscrollTest(kWheelScrollingModeNone) {}
+};
+
+class RenderWidgetHostViewAuraOverScrollAsyncWheelEventsEnabledTest
+    : public RenderWidgetHostViewAuraOverscrollTest {
+ public:
+  RenderWidgetHostViewAuraOverScrollAsyncWheelEventsEnabledTest()
+      : RenderWidgetHostViewAuraOverscrollTest(kAsyncWheelEvents) {}
 };
 
 class RenderWidgetHostViewAuraShutdownTest
     : public RenderWidgetHostViewAuraTest {
  public:
   RenderWidgetHostViewAuraShutdownTest() {}
 
   void TearDown() override {
     // No TearDownEnvironment here, we do this explicitly during the test.
   }
@@ skipping 2487 matching lines @@
       WebMouseWheelEvent::kPhaseBegan);  // sent directly
   SimulateWheelEventPossiblyIncludingPhase(
       !wheel_scroll_latching_enabled_, -60, 1, 0, false,
       WebMouseWheelEvent::kPhaseChanged);  // enqueued
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
 
   // Receive ACK the first wheel event as not processed.
   SendInputEventACK(WebInputEvent::kMouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEventsAfterMouseWheelACK(true, true);
+  ExpectGestureScrollEventsAfterMouseWheelACK(true, 1);
 
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEndForWheelScrolling(false);
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_delegate()->current_mode());
 
-  SendInputEventACK(WebInputEvent::kMouseWheel,
-                    INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEventsAfterMouseWheelACK(false, false);
+  if (wheel_scrolling_mode_ == kAsyncWheelEvents) {
+    ExpectGestureScrollUpdateAfterNonBlockingMouseWheelACK(true);
+  } else {
+    ExpectGestureScrollEndForWheelScrolling(false);
+    SendInputEventACK(WebInputEvent::kMouseWheel,
+                      INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+    ExpectGestureScrollEventsAfterMouseWheelACK(false, 0);
+  }
 
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  if (wheel_scroll_latching_enabled_) {
-    SimulateWheelEventWithPhase(0, 0, 0, false,
-                                WebMouseWheelEvent::kPhaseEnded);
+  if (wheel_scrolling_mode_ == kAsyncWheelEvents) {
+    SimulateWheelEventWithPhase(0, 0, 0, true, WebMouseWheelEvent::kPhaseEnded);
+    ExpectGestureScrollEndAfterNonBlockingMouseWheelACK();
+  } else if (wheel_scroll_latching_enabled_) {
+    SimulateWheelEventWithPhase(0, 0, 0, true, WebMouseWheelEvent::kPhaseEnded);
     EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
     SendInputEventACK(WebInputEvent::kMouseWheel,
                       INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+    ExpectGestureScrollEndForWheelScrolling(true);
+  } else {
+    ExpectGestureScrollEndForWheelScrolling(true);
   }
-  ExpectGestureScrollEndForWheelScrolling(true);
 
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_delegate()->current_mode());
 }
 TEST_F(RenderWidgetHostViewAuraOverscrollTest, WheelNotPreciseScrollEvent) {
   WheelNotPreciseScrollEvent();
 }
 TEST_F(RenderWidgetHostViewAuraOverscrollWithoutWheelScrollLatchingTest,
        WheelNotPreciseScrollEvent) {
   WheelNotPreciseScrollEvent();
 }
+TEST_F(RenderWidgetHostViewAuraOverScrollAsyncWheelEventsEnabledTest,
+       WheelNotPreciseScrollEvent) {
+  WheelNotPreciseScrollEvent();
+}
 
 void RenderWidgetHostViewAuraOverscrollTest::WheelScrollEventOverscrolls() {
   SetUpOverscrollEnvironment();
 
   // Simulate wheel events.
   SimulateWheelEventPossiblyIncludingPhase(
       !wheel_scroll_latching_enabled_, -5, 0, 0, true,
       WebMouseWheelEvent::kPhaseBegan);  // sent directly
   SimulateWheelEventPossiblyIncludingPhase(
       !wheel_scroll_latching_enabled_, -1, 1, 0, true,
       WebMouseWheelEvent::kPhaseChanged);  // enqueued
   SimulateWheelEventPossiblyIncludingPhase(
       !wheel_scroll_latching_enabled_, -10, -3, 0, true,
       WebMouseWheelEvent::kPhaseChanged);  // coalesced into previous event
   SimulateWheelEventPossiblyIncludingPhase(
       !wheel_scroll_latching_enabled_, -15, -1, 0, true,
       WebMouseWheelEvent::kPhaseChanged);  // coalesced into previous event
   SimulateWheelEventPossiblyIncludingPhase(
       !wheel_scroll_latching_enabled_, -30, -3, 0, true,
       WebMouseWheelEvent::kPhaseChanged);  // coalesced into previous event
   SimulateWheelEventPossiblyIncludingPhase(
       !wheel_scroll_latching_enabled_, -20, 6, 1, true,
       WebMouseWheelEvent::kPhaseChanged);  // enqueued, different modifiers
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
 
   // Receive ACK the first wheel event as not processed.
   SendInputEventACK(WebInputEvent::kMouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEventsAfterMouseWheelACK(true, true);
+  ExpectGestureScrollEventsAfterMouseWheelACK(true, 2);
 
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEndForWheelScrolling(false);
 
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_delegate()->current_mode());
-
-  // Receive ACK for the second (coalesced) event as not processed. This will
-  // start a back navigation. However, this will also cause the queued next
-  // event to be sent to the renderer. But since overscroll navigation has
-  // started, that event will also be included in the overscroll computation
-  // instead of being sent to the renderer. So the result will be an overscroll
-  // back navigation, and no ScrollUpdate event will be sent to the renderer.
-  SendInputEventACK(WebInputEvent::kMouseWheel,
-                    INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEventsAfterMouseWheelACK(false, true);
-
+  if (wheel_scrolling_mode_ == kAsyncWheelEvents) {
+    ExpectGestureScrollUpdateAfterNonBlockingMouseWheelACK(true);
+  } else {
+    ExpectGestureScrollEndForWheelScrolling(false);
+    // Receive ACK for the second (coalesced) event as not processed. This will
+    // start a back navigation. However, this will also cause the queued next
+    // event to be sent to the renderer. But since overscroll navigation has
+    // started, that event will also be included in the overscroll computation
+    // instead of being sent to the renderer. So the result will be an
+    // overscroll back navigation, and no ScrollUpdate event will be sent to the
+    // renderer.
+    SendInputEventACK(WebInputEvent::kMouseWheel,
+                      INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+    ExpectGestureScrollEventsAfterMouseWheelACK(false, 1);
+  }
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   ExpectGestureScrollEndForWheelScrolling(false);
 
   SendInputEventACK(WebInputEvent::kMouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   if (wheel_scroll_latching_enabled_) {
     EXPECT_EQ(0U, GetSentMessageCountAndResetSink());
   } else {
     // ScrollBegin and ScrollEnd will be queued events.
@@ skipping 13 matching lines @@
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_delegate()->current_mode());
   EXPECT_EQ(1U, sink_->message_count());
 }
 TEST_F(RenderWidgetHostViewAuraOverscrollTest, WheelScrollEventOverscrolls) {
   WheelScrollEventOverscrolls();
 }
 TEST_F(RenderWidgetHostViewAuraOverscrollWithoutWheelScrollLatchingTest,
        WheelScrollEventOverscrolls) {
   WheelScrollEventOverscrolls();
 }
+TEST_F(RenderWidgetHostViewAuraOverScrollAsyncWheelEventsEnabledTest,
+       WheelScrollEventOverscrolls) {
+  WheelScrollEventOverscrolls();
+}
 
 // Tests that if some scroll events are consumed towards the start, then
 // subsequent scrolls do not horizontal overscroll.
 void RenderWidgetHostViewAuraOverscrollTest::
     WheelScrollConsumedDoNotHorizOverscroll() {
   SetUpOverscrollEnvironment();
 
   // Simulate wheel events.
   SimulateWheelEventPossiblyIncludingPhase(
       !wheel_scroll_latching_enabled_, -5, 0, 0, true,
@@ skipping 13 matching lines @@
   SimulateWheelEventPossiblyIncludingPhase(
       !wheel_scroll_latching_enabled_, -20, 6, 1, true,
       WebMouseWheelEvent::kPhaseChanged);  // enqueued, different modifiers
 
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
 
   // Receive ACK the first wheel event as processed.
   SendInputEventACK(WebInputEvent::kMouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEventsAfterMouseWheelACK(true, true);
-
-  SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
-                    INPUT_EVENT_ACK_STATE_CONSUMED);
-  ExpectGestureScrollEndForWheelScrolling(false);
+  ExpectGestureScrollEventsAfterMouseWheelACK(true, 2);
 
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_delegate()->current_mode());
 
-  // Receive ACK for the second (coalesced) event as not processed. This should
-  // not initiate overscroll, since the beginning of the scroll has been
-  // consumed. The queued event with different modifiers should be sent to the
-  // renderer.
-  SendInputEventACK(WebInputEvent::kMouseWheel,
-                    INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+  if (wheel_scrolling_mode_ != kAsyncWheelEvents) {
+    SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
+                      INPUT_EVENT_ACK_STATE_CONSUMED);
+    ExpectGestureScrollEndForWheelScrolling(false);
+    // Receive ACK for the second (coalesced) event as not processed. This
+    // should not initiate overscroll, since the beginning of the scroll has
+    // been consumed. The queued event with different modifiers should be sent
+    // to the renderer.
+    SendInputEventACK(WebInputEvent::kMouseWheel,
+                      INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+    ExpectGestureScrollEventsAfterMouseWheelACK(false, 1);
+  }
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
-  ExpectGestureScrollEventsAfterMouseWheelACK(false, true);
+
+  if (wheel_scrolling_mode_ == kAsyncWheelEvents) {
+    // The first and second GSU events are coalesced. This is the ack for the
+    // coalesced event. Since it is the first GSU, the ack should be consumed.
+    SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
+                      INPUT_EVENT_ACK_STATE_CONSUMED);
+    ExpectGestureScrollUpdateAfterNonBlockingMouseWheelACK(true);
+  } else {
+    SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
+                      INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+    ExpectGestureScrollEndForWheelScrolling(false);
+    SendInputEventACK(WebInputEvent::kMouseWheel,
+                      INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+    ExpectGestureScrollEventsAfterMouseWheelACK(false, 0);
+  }
 
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEndForWheelScrolling(false);
-
-  SendInputEventACK(WebInputEvent::kMouseWheel,
-                    INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEventsAfterMouseWheelACK(false, false);
-
-  SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
-                    INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  if (wheel_scroll_latching_enabled_) {
+  if (wheel_scrolling_mode_ == kAsyncWheelEvents) {
+    SimulateWheelEventWithPhase(0, 0, 0, true, WebMouseWheelEvent::kPhaseEnded);
+    ExpectGestureScrollEndAfterNonBlockingMouseWheelACK();
+  } else if (wheel_scroll_latching_enabled_) {
     SimulateWheelEventWithPhase(0, 0, 0, true, WebMouseWheelEvent::kPhaseEnded);
     EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
     SendInputEventACK(WebInputEvent::kMouseWheel,
                       INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+    ExpectGestureScrollEndForWheelScrolling(true);
+  } else {
+    ExpectGestureScrollEndForWheelScrolling(true);
   }
-
-  ExpectGestureScrollEndForWheelScrolling(true);
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
 }
 TEST_F(RenderWidgetHostViewAuraOverscrollTest,
        WheelScrollConsumedDoNotHorizOverscroll) {
   WheelScrollConsumedDoNotHorizOverscroll();
 }
 TEST_F(RenderWidgetHostViewAuraOverscrollWithoutWheelScrollLatchingTest,
        WheelScrollConsumedDoNotHorizOverscroll) {
   WheelScrollConsumedDoNotHorizOverscroll();
 }
+TEST_F(RenderWidgetHostViewAuraOverScrollAsyncWheelEventsEnabledTest,
+       WheelScrollConsumedDoNotHorizOverscroll) {
+  WheelScrollConsumedDoNotHorizOverscroll();
+}
 
 // Tests that wheel-scrolling correctly turns overscroll on and off.
 void RenderWidgetHostViewAuraOverscrollTest::WheelScrollOverscrollToggle() {
   SetUpOverscrollEnvironment();
 
   // Send a wheel event. ACK the event as not processed. This should not
   // initiate an overscroll gesture since it doesn't cross the threshold yet.
   SimulateWheelEventPossiblyIncludingPhase(!wheel_scroll_latching_enabled_, 10,
                                            0, 0, true,
                                            WebMouseWheelEvent::kPhaseBegan);
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::kMouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEventsAfterMouseWheelACK(true, false);
+  ExpectGestureScrollEventsAfterMouseWheelACK(true, 0);
 
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   ExpectGestureScrollEndForWheelScrolling(false);
 
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_delegate()->current_mode());
 
   // Scroll some more so as to not overscroll.
   SimulateWheelEventPossiblyIncludingPhase(!wheel_scroll_latching_enabled_, 10,
                                            0, 0, true,
                                            WebMouseWheelEvent::kPhaseChanged);
-  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
-  SendInputEventACK(WebInputEvent::kMouseWheel,
-                    INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEventsAfterMouseWheelACK(false, false);
+  if (wheel_scrolling_mode_ == kAsyncWheelEvents) {
+    ExpectGestureScrollUpdateAfterNonBlockingMouseWheelACK(false);
+  } else {
+    EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
+    SendInputEventACK(WebInputEvent::kMouseWheel,
+                      INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+    ExpectGestureScrollEventsAfterMouseWheelACK(false, 0);
+  }
 
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   ExpectGestureScrollEndForWheelScrolling(false);
 
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_delegate()->current_mode());
 
   // Scroll some more to initiate an overscroll.
   SimulateWheelEventPossiblyIncludingPhase(!wheel_scroll_latching_enabled_, 40,
                                            0, 0, true,
                                            WebMouseWheelEvent::kPhaseChanged);
-  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
-  SendInputEventACK(WebInputEvent::kMouseWheel,
-                    INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEventsAfterMouseWheelACK(false, false);
+  if (wheel_scrolling_mode_ == kAsyncWheelEvents) {
+    ExpectGestureScrollUpdateAfterNonBlockingMouseWheelACK(false);
+  } else {
+    EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
+    SendInputEventACK(WebInputEvent::kMouseWheel,
+                      INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+    ExpectGestureScrollEventsAfterMouseWheelACK(false, 0);
+  }
 
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   ExpectGestureScrollEndForWheelScrolling(false);
 
   EXPECT_EQ(OVERSCROLL_EAST, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_EAST, overscroll_delegate()->current_mode());
   EXPECT_EQ(60.f, overscroll_delta_x());
   EXPECT_EQ(10.f, overscroll_delegate()->delta_x());
   EXPECT_EQ(0.f, overscroll_delegate()->delta_y());
@@ skipping 12 matching lines @@
     EXPECT_EQ(2U, GetSentMessageCountAndResetSink());
   }
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_delegate()->current_mode());
 
   // Continue to scroll in the reverse direction.
   SimulateWheelEventPossiblyIncludingPhase(!wheel_scroll_latching_enabled_, -20,
                                            0, 0, true,
                                            WebMouseWheelEvent::kPhaseChanged);
 
-  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
-  SendInputEventACK(WebInputEvent::kMouseWheel,
-                    INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEventsAfterMouseWheelACK(false, false);
+  if (wheel_scrolling_mode_ == kAsyncWheelEvents) {
+    ExpectGestureScrollUpdateAfterNonBlockingMouseWheelACK(false);
+  } else {
+    EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
+    SendInputEventACK(WebInputEvent::kMouseWheel,
+                      INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+    ExpectGestureScrollEventsAfterMouseWheelACK(false, 0);
+  }
 
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   ExpectGestureScrollEndForWheelScrolling(false);
 
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_delegate()->current_mode());
 
   // Continue to scroll in the reverse direction enough to initiate overscroll
   // in that direction.
   SimulateWheelEventPossiblyIncludingPhase(!wheel_scroll_latching_enabled_, -55,
                                            0, 0, true,
                                            WebMouseWheelEvent::kPhaseChanged);
-  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
-  SendInputEventACK(WebInputEvent::kMouseWheel,
-                    INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEventsAfterMouseWheelACK(false, false);
+  if (wheel_scrolling_mode_ == kAsyncWheelEvents) {
+    ExpectGestureScrollUpdateAfterNonBlockingMouseWheelACK(false);
+  } else {
+    EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
+    SendInputEventACK(WebInputEvent::kMouseWheel,
+                      INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+    ExpectGestureScrollEventsAfterMouseWheelACK(false, 0);
+  }
 
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  if (wheel_scroll_latching_enabled_) {
+  if (wheel_scrolling_mode_ == kAsyncWheelEvents) {
+    SimulateWheelEventWithPhase(0, 0, 0, true, WebMouseWheelEvent::kPhaseEnded);
+    ExpectGestureScrollEndAfterNonBlockingMouseWheelACK();
+  } else if (wheel_scroll_latching_enabled_) {
     SimulateWheelEventWithPhase(0, 0, 0, true, WebMouseWheelEvent::kPhaseEnded);
     EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
     SendInputEventACK(WebInputEvent::kMouseWheel,
                       INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+    ExpectGestureScrollEndForWheelScrolling(true);
+  } else {
+    ExpectGestureScrollEndForWheelScrolling(true);
   }
-  ExpectGestureScrollEndForWheelScrolling(true);
 
   EXPECT_EQ(OVERSCROLL_WEST, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_WEST, overscroll_delegate()->current_mode());
   EXPECT_EQ(-75.f, overscroll_delta_x());
   EXPECT_EQ(-25.f, overscroll_delegate()->delta_x());
   EXPECT_EQ(0.f, overscroll_delegate()->delta_y());
 }
 TEST_F(RenderWidgetHostViewAuraOverscrollTest, WheelScrollOverscrollToggle) {
   WheelScrollOverscrollToggle();
 }
 TEST_F(RenderWidgetHostViewAuraOverscrollWithoutWheelScrollLatchingTest,
        WheelScrollOverscrollToggle) {
   WheelScrollOverscrollToggle();
 }
+TEST_F(RenderWidgetHostViewAuraOverScrollAsyncWheelEventsEnabledTest,
+       WheelScrollOverscrollToggle) {
+  WheelScrollOverscrollToggle();
+}
 
 void RenderWidgetHostViewAuraOverscrollTest::ScrollEventsOverscrollWithFling() {
   SetUpOverscrollEnvironment();
 
   // Send a wheel event. ACK the event as not processed. This should not
   // initiate an overscroll gesture since it doesn't cross the threshold yet.
   SimulateWheelEventPossiblyIncludingPhase(!wheel_scroll_latching_enabled_, 10,
                                            0, 0, true,
                                            WebMouseWheelEvent::kPhaseBegan);
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::kMouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEventsAfterMouseWheelACK(true, false);
+  ExpectGestureScrollEventsAfterMouseWheelACK(true, 0);
 
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   ExpectGestureScrollEndForWheelScrolling(false);
 
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_delegate()->current_mode());
 
   // Scroll some more so as to not overscroll.
   SimulateWheelEventPossiblyIncludingPhase(!wheel_scroll_latching_enabled_, 20,
                                            0, 0, true,
                                            WebMouseWheelEvent::kPhaseChanged);
-  EXPECT_EQ(1U, sink_->message_count());
-  SendInputEventACK(WebInputEvent::kMouseWheel,
-                    INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+  if (wheel_scrolling_mode_ == kAsyncWheelEvents) {
+    ExpectGestureScrollUpdateAfterNonBlockingMouseWheelACK(false);
+  } else {
+    EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
+    SendInputEventACK(WebInputEvent::kMouseWheel,
+                      INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+    ExpectGestureScrollEventsAfterMouseWheelACK(false, 0);
+  }
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_delegate()->current_mode());
   sink_->ClearMessages();
 
   // Scroll some more to initiate an overscroll.
   SimulateWheelEventPossiblyIncludingPhase(!wheel_scroll_latching_enabled_, 30,
                                            0, 0, true,
                                            WebMouseWheelEvent::kPhaseChanged);
-  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
-  SendInputEventACK(WebInputEvent::kMouseWheel,
-                    INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEventsAfterMouseWheelACK(false, false);
-
+  if (wheel_scrolling_mode_ == kAsyncWheelEvents) {
+    ExpectGestureScrollUpdateAfterNonBlockingMouseWheelACK(false);
+  } else {
+    EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
+    SendInputEventACK(WebInputEvent::kMouseWheel,
+                      INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+    ExpectGestureScrollEventsAfterMouseWheelACK(false, 0);
+  }
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   ExpectGestureScrollEndForWheelScrolling(false);
 
   EXPECT_EQ(OVERSCROLL_EAST, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_EAST, overscroll_delegate()->current_mode());
 
   EXPECT_EQ(60.f, overscroll_delta_x());
   EXPECT_EQ(10.f, overscroll_delegate()->delta_x());
   EXPECT_EQ(0.f, overscroll_delegate()->delta_y());
@@ skipping 11 matching lines @@
   EXPECT_EQ(2U, sink_->message_count());
 }
 TEST_F(RenderWidgetHostViewAuraOverscrollTest,
        ScrollEventsOverscrollWithFling) {
   ScrollEventsOverscrollWithFling();
 }
 TEST_F(RenderWidgetHostViewAuraOverscrollWithoutWheelScrollLatchingTest,
        ScrollEventsOverscrollWithFling) {
   ScrollEventsOverscrollWithFling();
 }
+TEST_F(RenderWidgetHostViewAuraOverScrollAsyncWheelEventsEnabledTest,
+       ScrollEventsOverscrollWithFling) {
+  ScrollEventsOverscrollWithFling();
+}
 
 // Same as ScrollEventsOverscrollWithFling, but with zero velocity. Checks that
 // the zero-velocity fling does not reach the renderer.
 void RenderWidgetHostViewAuraOverscrollTest::
     ScrollEventsOverscrollWithZeroFling() {
   SetUpOverscrollEnvironment();
 
   // Send a wheel event. ACK the event as not processed. This should not
   // initiate an overscroll gesture since it doesn't cross the threshold yet.
   SimulateWheelEventPossiblyIncludingPhase(!wheel_scroll_latching_enabled_, 10,
                                            0, 0, true,
                                            WebMouseWheelEvent::kPhaseBegan);
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::kMouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEventsAfterMouseWheelACK(true, false);
+  ExpectGestureScrollEventsAfterMouseWheelACK(true, 0);
 
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   ExpectGestureScrollEndForWheelScrolling(false);
 
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_delegate()->current_mode());
 
   // Scroll some more so as to not overscroll.
   SimulateWheelEventPossiblyIncludingPhase(!wheel_scroll_latching_enabled_, 20,
                                            0, 0, true,
                                            WebMouseWheelEvent::kPhaseChanged);
-  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
-  SendInputEventACK(WebInputEvent::kMouseWheel,
-                    INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEventsAfterMouseWheelACK(false, false);
+  if (wheel_scrolling_mode_ == kAsyncWheelEvents) {
+    ExpectGestureScrollUpdateAfterNonBlockingMouseWheelACK(false);
+  } else {
+    EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
+    SendInputEventACK(WebInputEvent::kMouseWheel,
+                      INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+    ExpectGestureScrollEventsAfterMouseWheelACK(false, 0);
+  }
 
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   ExpectGestureScrollEndForWheelScrolling(false);
 
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_delegate()->current_mode());
 
   // Scroll some more to initiate an overscroll.
   SimulateWheelEventPossiblyIncludingPhase(!wheel_scroll_latching_enabled_, 30,
                                            0, 0, true,
                                            WebMouseWheelEvent::kPhaseChanged);
-  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
-  SendInputEventACK(WebInputEvent::kMouseWheel,
-                    INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEventsAfterMouseWheelACK(false, false);
+  if (wheel_scrolling_mode_ == kAsyncWheelEvents) {
+    ExpectGestureScrollUpdateAfterNonBlockingMouseWheelACK(false);
+  } else {
+    EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
+    SendInputEventACK(WebInputEvent::kMouseWheel,
+                      INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+    ExpectGestureScrollEventsAfterMouseWheelACK(false, 0);
+  }
 
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   ExpectGestureScrollEndForWheelScrolling(false);
 
   EXPECT_EQ(OVERSCROLL_EAST, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_EAST, overscroll_delegate()->current_mode());
 
   EXPECT_EQ(60.f, overscroll_delta_x());
   EXPECT_EQ(10.f, overscroll_delegate()->delta_x());
@@ skipping 12 matching lines @@
     EXPECT_EQ(2U, sink_->message_count());
 }
 TEST_F(RenderWidgetHostViewAuraOverscrollTest,
        ScrollEventsOverscrollWithZeroFling) {
   ScrollEventsOverscrollWithZeroFling();
 }
 TEST_F(RenderWidgetHostViewAuraOverscrollWithoutWheelScrollLatchingTest,
        ScrollEventsOverscrollWithZeroFling) {
   ScrollEventsOverscrollWithZeroFling();
 }
+TEST_F(RenderWidgetHostViewAuraOverScrollAsyncWheelEventsEnabledTest,
+       ScrollEventsOverscrollWithZeroFling) {
+  ScrollEventsOverscrollWithZeroFling();
+}
 
 // Tests that a fling in the opposite direction of the overscroll cancels the
 // overscroll nav instead of completing it.
 TEST_F(RenderWidgetHostViewAuraOverscrollTest, ReverseFlingCancelsOverscroll) {
   SetUpOverscrollEnvironment();
 
   {
     // Start and end a gesture in the same direction without processing the
     // gesture events in the renderer. This should initiate and complete an
     // overscroll navigation.
@@ skipping 437 matching lines @@
     OverscrollDirectionChangeMouseWheel() {
   SetUpOverscrollEnvironment();
 
   // Send wheel event and receive ack as not consumed.
   SimulateWheelEventPossiblyIncludingPhase(!wheel_scroll_latching_enabled_, 125,
                                            -5, 0, true,
                                            WebMouseWheelEvent::kPhaseBegan);
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::kMouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEventsAfterMouseWheelACK(true, false);
+  ExpectGestureScrollEventsAfterMouseWheelACK(true, 0);
 
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   ExpectGestureScrollEndForWheelScrolling(false);
 
   EXPECT_EQ(OVERSCROLL_EAST, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_EAST, overscroll_delegate()->current_mode());
 
   // Send another wheel event, but in the reverse direction. The overscroll
   // controller will not consume the event, because it is not triggering
   // gesture-nav.
 
   SimulateWheelEventPossiblyIncludingPhase(!wheel_scroll_latching_enabled_,
                                            -260, 0, 0, true,
                                            WebMouseWheelEvent::kPhaseChanged);
-  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
-  SendInputEventACK(WebInputEvent::kMouseWheel,
-                    INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEventsAfterMouseWheelACK(false, false);
+  if (wheel_scrolling_mode_ == kAsyncWheelEvents) {
+    ExpectGestureScrollUpdateAfterNonBlockingMouseWheelACK(false);
+  } else {
+    EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
+    SendInputEventACK(WebInputEvent::kMouseWheel,
+                      INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+    ExpectGestureScrollEventsAfterMouseWheelACK(false, 0);
+  }
+
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
 
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   ExpectGestureScrollEndForWheelScrolling(false);
 
   // Since it was unhandled; the overscroll should now be west
   EXPECT_EQ(OVERSCROLL_WEST, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_WEST, overscroll_delegate()->current_mode());
 
   SimulateWheelEventPossiblyIncludingPhase(!wheel_scroll_latching_enabled_, -20,
                                            0, 0, true,
                                            WebMouseWheelEvent::kPhaseChanged);
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
-  SendInputEventACK(WebInputEvent::kMouseWheel,
-                    INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+  if (wheel_scrolling_mode_ != kAsyncWheelEvents) {
+    SendInputEventACK(WebInputEvent::kMouseWheel,
+                      INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+  }
 
   // wheel event ack generates gesture scroll update; which gets consumed
   // solely by the overflow controller.
   if (!wheel_scroll_latching_enabled_) {
     // No ScrollUpdates, only ScrollBegin and ScrollEnd will be queued events.
     EXPECT_EQ(2U, GetSentMessageCountAndResetSink());
   } else {
     EXPECT_EQ(0U, GetSentMessageCountAndResetSink());
   }
 
   EXPECT_EQ(OVERSCROLL_WEST, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_WEST, overscroll_delegate()->current_mode());
 }
 TEST_F(RenderWidgetHostViewAuraOverscrollTest,
        OverscrollDirectionChangeMouseWheel) {
   OverscrollDirectionChangeMouseWheel();
 }
 TEST_F(RenderWidgetHostViewAuraOverscrollWithoutWheelScrollLatchingTest,
        OverscrollDirectionChangeMouseWheel) {
   OverscrollDirectionChangeMouseWheel();
 }
+TEST_F(RenderWidgetHostViewAuraOverScrollAsyncWheelEventsEnabledTest,
+       OverscrollDirectionChangeMouseWheel) {
+  OverscrollDirectionChangeMouseWheel();
+}
 
 void RenderWidgetHostViewAuraOverscrollTest::OverscrollMouseMoveCompletion() {
   SetUpOverscrollEnvironment();
 
   SimulateWheelEventPossiblyIncludingPhase(
       !wheel_scroll_latching_enabled_, 5, 0, 0, true,
       WebMouseWheelEvent::kPhaseBegan);  // sent directly
   SimulateWheelEventPossiblyIncludingPhase(
       !wheel_scroll_latching_enabled_, -1, 0, 0, true,
       WebMouseWheelEvent::kPhaseChanged);  // enqueued
   SimulateWheelEventPossiblyIncludingPhase(
       !wheel_scroll_latching_enabled_, -10, -3, 0, true,
       WebMouseWheelEvent::kPhaseChanged);  // coalesced into previous event
   SimulateWheelEventPossiblyIncludingPhase(
       !wheel_scroll_latching_enabled_, -15, -1, 0, true,
       WebMouseWheelEvent::kPhaseChanged);  // coalesced into previous event
   SimulateWheelEventPossiblyIncludingPhase(
       !wheel_scroll_latching_enabled_, -30, -3, 0, true,
       WebMouseWheelEvent::kPhaseChanged);  // coalesced into previous event
 
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
 
   // Receive ACK the first wheel event as not processed.
   SendInputEventACK(WebInputEvent::kMouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEventsAfterMouseWheelACK(true, true);
+  ExpectGestureScrollEventsAfterMouseWheelACK(true, 1);
 
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEndForWheelScrolling(false);
 
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_delegate()->current_mode());
 
-  // Receive ACK for the second (coalesced) event as not processed. This will
-  // start an overcroll gesture.
-  SendInputEventACK(WebInputEvent::kMouseWheel,
-                    INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEventsAfterMouseWheelACK(false, false);
+  if (wheel_scrolling_mode_ == kAsyncWheelEvents) {
+    ExpectGestureScrollUpdateAfterNonBlockingMouseWheelACK(true);
+  } else {
+    ExpectGestureScrollEndForWheelScrolling(false);
+    // Receive ACK for the second (coalesced) event as not processed. This will
+    // start an overcroll gesture.
+    SendInputEventACK(WebInputEvent::kMouseWheel,
+                      INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+    ExpectGestureScrollEventsAfterMouseWheelACK(false, 0);
+  }
 
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   ExpectGestureScrollEndForWheelScrolling(false);
 
   EXPECT_EQ(OVERSCROLL_WEST, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_WEST, overscroll_delegate()->current_mode());
 
   // Send a mouse-move event. This should cancel the overscroll navigation
   // (since the amount overscrolled is not above the threshold), and so the
@@ skipping 46 matching lines @@
   SendInputEventACK(WebInputEvent::kMouseMove,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
 }
 TEST_F(RenderWidgetHostViewAuraOverscrollTest, OverscrollMouseMoveCompletion) {
   OverscrollMouseMoveCompletion();
 }
 TEST_F(RenderWidgetHostViewAuraOverscrollWithoutWheelScrollLatchingTest,
        OverscrollMouseMoveCompletion) {
   OverscrollMouseMoveCompletion();
 }
+TEST_F(RenderWidgetHostViewAuraOverScrollAsyncWheelEventsEnabledTest,
+       OverscrollMouseMoveCompletion) {
+  OverscrollMouseMoveCompletion();
+}
 
 // Tests that if a page scrolled, then the overscroll controller's states are
 // reset after the end of the scroll.
 void RenderWidgetHostViewAuraOverscrollTest::
     OverscrollStateResetsAfterScroll() {
   SetUpOverscrollEnvironment();
 
   SimulateWheelEventPossiblyIncludingPhase(
       !wheel_scroll_latching_enabled_, 0, 5, 0, true,
       WebMouseWheelEvent::kPhaseBegan);  // sent directly
   SimulateWheelEventPossiblyIncludingPhase(
       !wheel_scroll_latching_enabled_, 0, 30, 0, true,
       WebMouseWheelEvent::kPhaseChanged);  // enqueued
   SimulateWheelEventPossiblyIncludingPhase(
       !wheel_scroll_latching_enabled_, 0, 40, 0, true,
       WebMouseWheelEvent::kPhaseChanged);  // coalesced into previous event
   SimulateWheelEventPossiblyIncludingPhase(
       !wheel_scroll_latching_enabled_, 0, 10, 0, true,
       WebMouseWheelEvent::kPhaseChanged);  // coalesced into previous event
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
 
   // The first wheel event is consumed. Dispatches the queued wheel event.
   SendInputEventACK(WebInputEvent::kMouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEventsAfterMouseWheelACK(true, true);
+  ExpectGestureScrollEventsAfterMouseWheelACK(true, 1);
 
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_CONSUMED);
-  ExpectGestureScrollEndForWheelScrolling(false);
   EXPECT_TRUE(ScrollStateIsContentScrolling());
 
-  // The second wheel event is consumed.
-  SendInputEventACK(WebInputEvent::kMouseWheel,
-                    INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEventsAfterMouseWheelACK(false, false);
+  if (wheel_scrolling_mode_ == kAsyncWheelEvents) {
+    ExpectGestureScrollUpdateAfterNonBlockingMouseWheelACK(true);
+  } else {
+    ExpectGestureScrollEndForWheelScrolling(false);
+    // The second wheel event is consumed.
+    SendInputEventACK(WebInputEvent::kMouseWheel,
+                      INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+    ExpectGestureScrollEventsAfterMouseWheelACK(false, 0);
+  }
 
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_CONSUMED);
 
-  if (wheel_scroll_latching_enabled_) {
+  if (wheel_scrolling_mode_ == kAsyncWheelEvents) {
+    SimulateWheelEventWithPhase(0, 0, 0, true, WebMouseWheelEvent::kPhaseEnded);
+    ExpectGestureScrollEndAfterNonBlockingMouseWheelACK();
+  } else if (wheel_scroll_latching_enabled_) {
     SimulateWheelEventWithPhase(0, 0, 0, true, WebMouseWheelEvent::kPhaseEnded);
     EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
     SendInputEventACK(WebInputEvent::kMouseWheel,
                       INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+    ExpectGestureScrollEndForWheelScrolling(true);
+  } else {
+    ExpectGestureScrollEndForWheelScrolling(true);
   }
-  ExpectGestureScrollEndForWheelScrolling(true);
   EXPECT_TRUE(ScrollStateIsContentScrolling());
 
-  // Touchpad scroll can end with a zero-velocity fling. But it is not
-  // dispatched, but it should still reset the overscroll controller state.
+  // Touchpad scroll can end with a zero-velocity fling which is not dispatched,
+  // but it should still reset the overscroll controller state.
   SimulateGestureEvent(WebInputEvent::kGestureScrollBegin,
                        blink::kWebGestureDeviceTouchscreen);
   SimulateGestureFlingStartEvent(0.f, 0.f, blink::kWebGestureDeviceTouchpad);
   EXPECT_TRUE(ScrollStateIsUnknown());
   // ScrollBegin will be queued events.
   EXPECT_EQ(1U, sink_->message_count());
 
   // Dropped flings should neither propagate *nor* indicate that they were
   // consumed and have triggered a fling animation (as tracked by the router).
   EXPECT_FALSE(parent_host_->input_router()->HasPendingEvents());
@@ skipping 13 matching lines @@
       !wheel_scroll_latching_enabled_, -100, 0, 0, true,
       WebMouseWheelEvent::kPhaseChanged);  // coalesced into previous event
 
   EXPECT_TRUE(ScrollStateIsUnknown());
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
 
   // The first wheel scroll did not scroll content. Overscroll should not start
   // yet, since enough hasn't been scrolled.
   SendInputEventACK(WebInputEvent::kMouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEventsAfterMouseWheelACK(true, true);
-
-  SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
-                    INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEndForWheelScrolling(false);
-  EXPECT_TRUE(ScrollStateIsUnknown());
-
-  SendInputEventACK(WebInputEvent::kMouseWheel,
-                    INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  ExpectGestureScrollEventsAfterMouseWheelACK(false, false);
+  ExpectGestureScrollEventsAfterMouseWheelACK(true, 1);
 
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
 
-  if (wheel_scroll_latching_enabled_) {
+  EXPECT_TRUE(ScrollStateIsUnknown());
+
+  if (wheel_scrolling_mode_ == kAsyncWheelEvents) {
+    ExpectGestureScrollUpdateAfterNonBlockingMouseWheelACK(true);
+  } else {
+    ExpectGestureScrollEndForWheelScrolling(false);
+    SendInputEventACK(WebInputEvent::kMouseWheel,
+                      INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+    ExpectGestureScrollEventsAfterMouseWheelACK(false, 0);
+  }
+
+  SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
+                    INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+
+  if (wheel_scrolling_mode_ == kAsyncWheelEvents) {
+    SimulateWheelEventWithPhase(0, 0, 0, true, WebMouseWheelEvent::kPhaseEnded);
+    ExpectGestureScrollEndAfterNonBlockingMouseWheelACK();
+  } else if (wheel_scroll_latching_enabled_) {
     SimulateWheelEventWithPhase(0, 0, 0, true, WebMouseWheelEvent::kPhaseEnded);
     EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
     SendInputEventACK(WebInputEvent::kMouseWheel,
                       INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+    ExpectGestureScrollEndForWheelScrolling(true);
+  } else {
+    ExpectGestureScrollEndForWheelScrolling(true);
   }
-
-  ExpectGestureScrollEndForWheelScrolling(true);
   EXPECT_EQ(OVERSCROLL_WEST, overscroll_mode());
   EXPECT_TRUE(ScrollStateIsOverscrolling());
 
   // The GestureScrollBegin will reset the delegate's mode, so check it here.
   EXPECT_EQ(OVERSCROLL_WEST, overscroll_delegate()->current_mode());
   SimulateGestureEvent(WebInputEvent::kGestureScrollBegin,
                        blink::kWebGestureDeviceTouchscreen);
   SimulateGestureFlingStartEvent(0.f, 0.f, blink::kWebGestureDeviceTouchpad);
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_TRUE(ScrollStateIsUnknown());
   // ScrollBegin will be the queued event.
   EXPECT_EQ(1U, sink_->message_count());
   EXPECT_FALSE(parent_host_->input_router()->HasPendingEvents());
 }
 TEST_F(RenderWidgetHostViewAuraOverscrollTest,
        OverscrollStateResetsAfterScroll) {
   OverscrollStateResetsAfterScroll();
 }
 TEST_F(RenderWidgetHostViewAuraOverscrollWithoutWheelScrollLatchingTest,
        OverscrollStateResetsAfterScroll) {
   OverscrollStateResetsAfterScroll();
 }
+TEST_F(RenderWidgetHostViewAuraOverScrollAsyncWheelEventsEnabledTest,
+       OverscrollStateResetsAfterScroll) {
+  OverscrollStateResetsAfterScroll();
+}
 
 TEST_F(RenderWidgetHostViewAuraOverscrollTest, OverscrollResetsOnBlur) {
   SetUpOverscrollEnvironment();
 
   // Start an overscroll with gesture scroll. In the middle of the scroll, blur
   // the host.
   SimulateGestureEvent(WebInputEvent::kGestureScrollBegin,
                        blink::kWebGestureDeviceTouchscreen);
   SimulateGestureScrollUpdateEvent(300, -5, 0);
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
@@ skipping 225 matching lines @@
   view_->OnTouchEvent(&press2);
   SendTouchEventACK(blink::WebInputEvent::kTouchStart,
                     INPUT_EVENT_ACK_STATE_CONSUMED, press2.unique_event_id());
 
   EXPECT_EQ(2U, view_->dispatcher_->GetAndResetProcessedTouchEventCount());
 }
 
 // Tests that the scroll deltas stored within the overscroll controller get
 // reset at the end of the overscroll gesture even if the overscroll threshold
 // isn't surpassed and the overscroll mode stays OVERSCROLL_NONE.
-TEST_F(RenderWidgetHostViewAuraOverscrollTest, ScrollDeltasResetOnEnd) {
+void RenderWidgetHostViewAuraOverscrollTest::ScrollDeltasResetOnEnd() {
   SetUpOverscrollEnvironment();
   // Wheel event scroll ending with mouse move.
-  SimulateWheelEvent(-30, -10, 0, true);  // sent directly
+  SimulateWheelEventPossiblyIncludingPhase(
+      !wheel_scroll_latching_enabled_, -30, -10, 0, true,
+      WebMouseWheelEvent::kPhaseBegan);  // sent directly
   SendInputEventACK(WebInputEvent::kMouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(-30.f, overscroll_delta_x());
   EXPECT_EQ(-10.f, overscroll_delta_y());
   SimulateMouseMove(5, 10, 0);
   EXPECT_EQ(0.f, overscroll_delta_x());
   EXPECT_EQ(0.f, overscroll_delta_y());
 
   // Scroll gesture.
   SimulateGestureEvent(WebInputEvent::kGestureScrollBegin,
                        blink::kWebGestureDeviceTouchscreen);
   SimulateGestureScrollUpdateEvent(-30, -5, 0);
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(-30.f, overscroll_delta_x());
   EXPECT_EQ(-5.f, overscroll_delta_y());
   SimulateGestureEvent(WebInputEvent::kGestureScrollEnd,
                        blink::kWebGestureDeviceTouchscreen);
   EXPECT_EQ(0.f, overscroll_delta_x());
   EXPECT_EQ(0.f, overscroll_delta_y());
 
   // Wheel event scroll ending with a fling.
-  SimulateWheelEvent(5, 0, 0, true);
-  SendInputEventACK(WebInputEvent::kMouseWheel,
-                    INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+  SimulateWheelEventPossiblyIncludingPhase(!wheel_scroll_latching_enabled_, 5,
+                                           0, 0, true,
+                                           WebMouseWheelEvent::kPhaseChanged);
+  if (wheel_scrolling_mode_ != kAsyncWheelEvents) {
+    SendInputEventACK(WebInputEvent::kMouseWheel,
+                      INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+  }
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  SimulateWheelEvent(10, -5, 0, true);
-  SendInputEventACK(WebInputEvent::kMouseWheel,
-                    INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+  SimulateWheelEventPossiblyIncludingPhase(!wheel_scroll_latching_enabled_, 10,
+                                           -5, 0, true,
+                                           WebMouseWheelEvent::kPhaseChanged);
+  if (wheel_scrolling_mode_ != kAsyncWheelEvents) {
+    SendInputEventACK(WebInputEvent::kMouseWheel,
+                      INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+  }
   SendInputEventACK(WebInputEvent::kGestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(15.f, overscroll_delta_x());
   EXPECT_EQ(-5.f, overscroll_delta_y());
   SimulateGestureEvent(WebInputEvent::kGestureScrollBegin,
                        blink::kWebGestureDeviceTouchscreen);
   SimulateGestureFlingStartEvent(0.f, 0.1f, blink::kWebGestureDeviceTouchpad);
   EXPECT_EQ(0.f, overscroll_delta_x());
   EXPECT_EQ(0.f, overscroll_delta_y());
 }
+TEST_F(RenderWidgetHostViewAuraOverscrollTest, ScrollDeltasResetOnEnd) {
+  ScrollDeltasResetOnEnd();
+}
+TEST_F(RenderWidgetHostViewAuraOverscrollWithoutWheelScrollLatchingTest,
+       ScrollDeltasResetOnEnd) {
+  ScrollDeltasResetOnEnd();
+}
+TEST_F(RenderWidgetHostViewAuraOverScrollAsyncWheelEventsEnabledTest,
+       ScrollDeltasResetOnEnd) {
+  ScrollDeltasResetOnEnd();
+}
 
 TEST_F(RenderWidgetHostViewAuraTest, ForwardMouseEvent) {
   aura::Window* root = parent_view_->GetNativeView()->GetRootWindow();
 
   // Set up test delegate and window hierarchy.
   aura::test::EventCountDelegate delegate;
   std::unique_ptr<aura::Window> parent(new aura::Window(&delegate));
   parent->Init(ui::LAYER_TEXTURED);
   root->AddChild(parent.get());
   view_->InitAsChild(parent.get());
@@ skipping 588 matching lines @@
     // There is no composition in the beginning.
     EXPECT_FALSE(has_composition_text());
     SetHasCompositionTextToTrue();
     view->ImeCancelComposition();
     // The composition must have been canceled.
     EXPECT_FALSE(has_composition_text());
   }
 }
 
 }  // namespace content