MouseWheelEventQueue sends scrollEnd right away when latching is disabled.

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 3202 matching lines @@
   // Simulate wheel events.
   SimulateWheelEvent(-5, 0, 0, false);    // sent directly
   SimulateWheelEvent(-60, 1, 0, false);    // enqueued
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
 
   // Receive ACK the first wheel event as not processed.
   SendInputEventACK(WebInputEvent::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
 
-  // ScrollBegin, ScrollUpdate, MouseWheel will be queued events
+  // ScrollBegin, ScrollUpdate, and MouseWheel will be queued events.
   EXPECT_EQ(3U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::GestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
 
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_delegate()->current_mode());
+  // ScrollEnd will be the queued event.
+  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
 
   SendInputEventACK(WebInputEvent::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  // ScrollUpdate, MouseWheel will be queued events
-  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
+  // ScrollBegin and ScrollUpdate will be queued events.
+  EXPECT_EQ(2U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::GestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
 
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_delegate()->current_mode());
+  // ScrollEnd will be the queued event.
+  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
 }
 
 TEST_F(RenderWidgetHostViewAuraOverscrollTest, WheelScrollEventOverscrolls) {
   SetUpOverscrollEnvironment();
 
   // Simulate wheel events.
   SimulateWheelEvent(-5, 0, 0, true);    // sent directly
   SimulateWheelEvent(-1, 1, 0, true);    // enqueued
   SimulateWheelEvent(-10, -3, 0, true);  // coalesced into previous event
   SimulateWheelEvent(-15, -1, 0, true);  // coalesced into previous event
   SimulateWheelEvent(-30, -3, 0, true);  // coalesced into previous event
   SimulateWheelEvent(-20, 6, 1, true);   // enqueued, different modifiers
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
 
   // Receive ACK the first wheel event as not processed.
   SendInputEventACK(WebInputEvent::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
 
-  // ScrollBegin, ScrollUpdate, MouseWheel will be queued events
+  // ScrollBegin, ScrollUpdate, and MouseWheel will be queued events.
   EXPECT_EQ(3U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::GestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
 
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_delegate()->current_mode());
+  // ScrollEnd will be the queued event.
+  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
 
   // 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 event will be sent to the renderer.
+  // back navigation, and no ScrollUpdate event will be sent to the renderer.
   SendInputEventACK(WebInputEvent::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  // ScrollUpdate, MouseWheel will be queued events
-  EXPECT_EQ(2U, GetSentMessageCountAndResetSink());
+  // ScrollBegin, ScrollUpdate, and MouseWheel will be queued events.
+  EXPECT_EQ(3U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::GestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+  // ScrollEnd will be the queued event.
+  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
+
   SendInputEventACK(WebInputEvent::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+  // ScrollBegin and ScrollEnd will be queued events.
+  EXPECT_EQ(2U, GetSentMessageCountAndResetSink());
 
   EXPECT_EQ(OVERSCROLL_WEST, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_WEST, overscroll_delegate()->current_mode());
   EXPECT_EQ(-81.f, overscroll_delta_x());
   EXPECT_EQ(-31.f, overscroll_delegate()->delta_x());
   EXPECT_EQ(0.f, overscroll_delegate()->delta_y());
   EXPECT_EQ(0U, sink_->message_count());
 
   // Send a mouse-move event. This should cancel the overscroll navigation.
   SimulateMouseMove(5, 10, 0);
@@ skipping 14 matching lines @@
   SimulateWheelEvent(-10, -3, 0, true);  // coalesced into previous event
   SimulateWheelEvent(-15, -1, 0, true);  // coalesced into previous event
   SimulateWheelEvent(-30, -3, 0, true);  // coalesced into previous event
   SimulateWheelEvent(-20, 6, 1, true);   // enqueued, different modifiers
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
 
   // Receive ACK the first wheel event as processed.
   SendInputEventACK(WebInputEvent::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  // ScrollBegin, ScrollUpdate, MouseWheel will be queued events
+  // ScrollBegin, ScrollUpdate, and MouseWheel will be queued events.
   EXPECT_EQ(3U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::GestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_CONSUMED);
+  // ScrollEnd will be the queued event.
+  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
 
   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::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
-  // ScrollUpdate, MouseWheel will be queued events
+  // ScrollBegin, ScrollUpdate, and MouseWheel will be queued events.
+  EXPECT_EQ(3U, GetSentMessageCountAndResetSink());
+  SendInputEventACK(WebInputEvent::GestureScrollUpdate,
+                    INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+  // ScrollEnd will be the queued event.
+  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
+
+  SendInputEventACK(WebInputEvent::MouseWheel,
+                    INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+  // ScrollBegin, ScrollUpdate, and MouseWheel will be queued events.
   EXPECT_EQ(2U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::GestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-
-  SendInputEventACK(WebInputEvent::MouseWheel,
-                    INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  // ScrollUpdate will be queued events
+  // ScrollEnd will be the queued event.
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
-  SendInputEventACK(WebInputEvent::GestureScrollUpdate,
-                    INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-
-  EXPECT_EQ(0U, sink_->message_count());
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
 }
 
 // Tests that wheel-scrolling correctly turns overscroll on and off.
 TEST_F(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.
   SimulateWheelEvent(10, 0, 0, true);
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+  // ScrollBegin and ScrollUpdate will be queued events.
   EXPECT_EQ(2U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::GestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+  // ScrollEnd will be the queued event.
+  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_delegate()->current_mode());
 
   // Scroll some more so as to not overscroll.
   SimulateWheelEvent(10, 0, 0, true);
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
+  // ScrollBegin and ScrollUpdate will be queued events.
+  EXPECT_EQ(2U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::GestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+  // ScrollEnd will be the queued event.
+  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_delegate()->current_mode());
 
   // Scroll some more to initiate an overscroll.
   SimulateWheelEvent(40, 0, 0, true);
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
+  // ScrollBegin and ScrollUpdate will be queued events.
+  EXPECT_EQ(2U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::GestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+  // ScrollEnd will be the queued event.
+  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
   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());
 
   // Scroll in the reverse direction enough to abort the overscroll.
   SimulateWheelEvent(-20, 0, 0, true);
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  EXPECT_EQ(0U, sink_->message_count());
+  // ScrollBegin and ScrollEnd will be queued events.
+  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.
   SimulateWheelEvent(-20, 0, 0, true);
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
+  // ScrollBegin and ScrollUpdate will be queued events.
+  EXPECT_EQ(2U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::GestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  EXPECT_EQ(0U, GetSentMessageCountAndResetSink());
+  // ScrollEnd will be the queued event.
+  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
   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.
   SimulateWheelEvent(-55, 0, 0, true);
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
+  // ScrollBegin and ScrollUpdate will be the queued events.
+  EXPECT_EQ(2U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::GestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  EXPECT_EQ(0U, GetSentMessageCountAndResetSink());
+  // ScrollEnd will be the queued event.
+  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
   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,
        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.
   SimulateWheelEvent(10, 0, 0, true);
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+  // ScrollBegin and ScrollUpdate will be queued events.
   EXPECT_EQ(2U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::GestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_delegate()->current_mode());
-  EXPECT_EQ(0U, GetSentMessageCountAndResetSink());
+  // ScrollEnd will be the queued event.
+  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
 
   // Scroll some more so as to not overscroll.
   SimulateWheelEvent(20, 0, 0, true);
   EXPECT_EQ(1U, sink_->message_count());
   SendInputEventACK(WebInputEvent::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   SendInputEventACK(WebInputEvent::GestureScrollUpdate,
                     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.
   SimulateWheelEvent(30, 0, 0, true);
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   SendInputEventACK(WebInputEvent::GestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
+  // ScrollBegin, ScrollUpdate, and ScrollEnd will be queued events.
+  EXPECT_EQ(3U, GetSentMessageCountAndResetSink());
   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());
   EXPECT_EQ(0U, GetSentMessageCountAndResetSink());
 
   // Send a fling start, but with a small velocity, so that the overscroll is
   // aborted. The fling should proceed to the renderer, through the gesture
   // event filter.
   SimulateGestureEvent(WebInputEvent::GestureScrollBegin,
                        blink::WebGestureDeviceTouchscreen);
   SimulateGestureFlingStartEvent(0.f, 0.1f, blink::WebGestureDeviceTouchpad);
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
-  EXPECT_EQ(3U, sink_->message_count());
+  // ScrollBegin and FlingStart will be queued events.
+  EXPECT_EQ(2U, sink_->message_count());
 }
 
 // Same as ScrollEventsOverscrollWithFling, but with zero velocity. Checks that
 // the zero-velocity fling does not reach the renderer.
 TEST_F(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.
   SimulateWheelEvent(10, 0, 0, true);
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+  // ScrollBegin and ScrollUpdate will be queued events.
   EXPECT_EQ(2U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::GestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_delegate()->current_mode());
-  EXPECT_EQ(0U, GetSentMessageCountAndResetSink());
+  // ScrollEnd will be the queued event.
+  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
 
   // Scroll some more so as to not overscroll.
   SimulateWheelEvent(20, 0, 0, true);
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
+  // ScrollBegin and ScrollUpdate will be queued events.
+  EXPECT_EQ(2U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::GestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_delegate()->current_mode());
+  // ScrollEnd will be the queued event.
+  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
 
   // Scroll some more to initiate an overscroll.
   SimulateWheelEvent(30, 0, 0, true);
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
+  // ScrollBegin and ScrollUpdate will be queued events.
+  EXPECT_EQ(2U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::GestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   EXPECT_EQ(OVERSCROLL_EAST, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_EAST, overscroll_delegate()->current_mode());
+  // ScrollEnd will be the queued event.
+  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
+
   EXPECT_EQ(60.f, overscroll_delta_x());
   EXPECT_EQ(10.f, overscroll_delegate()->delta_x());
   EXPECT_EQ(0.f, overscroll_delegate()->delta_y());
   EXPECT_EQ(0U, GetSentMessageCountAndResetSink());
 
   // Send a fling start, but with a small velocity, so that the overscroll is
   // aborted. The fling should proceed to the renderer, through the gesture
   // event filter.
   SimulateGestureEvent(WebInputEvent::GestureScrollBegin,
                        blink::WebGestureDeviceTouchscreen);
   SimulateGestureFlingStartEvent(10.f, 0.f, blink::WebGestureDeviceTouchpad);
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
-  EXPECT_EQ(3U, sink_->message_count());
+  // scrollBeign and FlingStart will be queued events.
+  EXPECT_EQ(2U, sink_->message_count());
 }
 
 // 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
@@ skipping 436 matching lines @@
 
 TEST_F(RenderWidgetHostViewAuraOverscrollTest,
        OverscrollDirectionChangeMouseWheel) {
   SetUpOverscrollEnvironment();
 
   // Send wheel event and receive ack as not consumed.
   SimulateWheelEvent(125, -5, 0, true);
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-
-  // ScrollBegin, ScrollUpdate messages.
+  // ScrollBegin and ScrollUpdate will be queued events.
   EXPECT_EQ(2U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::GestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   EXPECT_EQ(OVERSCROLL_EAST, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_EAST, overscroll_delegate()->current_mode());
+  // ScrollEnd will be the queued event.
+  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
 
   // Send another wheel event, but in the reverse direction. The overscroll
   // controller will not consume the event, because it is not triggering
   // gesture-nav.
 
   SimulateWheelEvent(-260, 0, 0, true);
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
-  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
+  // ScrollBegin and ScrollUpdate will be queued events.
+  EXPECT_EQ(2U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::GestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
 
   // Since it was unhandled; the overscroll should now be west
   EXPECT_EQ(OVERSCROLL_WEST, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_WEST, overscroll_delegate()->current_mode());
+  // ScrollEnd will be the queued event.
+  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
 
   SimulateWheelEvent(-20, 0, 0, true);
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
 
   // wheel event ack generates gesture scroll update; which gets consumed
   // solely by the overflow controller.
-  EXPECT_EQ(0U, GetSentMessageCountAndResetSink());
+  // No ScrollUpdates, only ScrollBegin and ScrollEnd will be queued events.
+  EXPECT_EQ(2U, GetSentMessageCountAndResetSink());
   EXPECT_EQ(OVERSCROLL_WEST, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_WEST, overscroll_delegate()->current_mode());
 }
 
 TEST_F(RenderWidgetHostViewAuraOverscrollTest, OverscrollMouseMoveCompletion) {
   SetUpOverscrollEnvironment();
 
   SimulateWheelEvent(5, 0, 0, true);     // sent directly
   SimulateWheelEvent(-1, 0, 0, true);    // enqueued
   SimulateWheelEvent(-10, -3, 0, true);  // coalesced into previous event
   SimulateWheelEvent(-15, -1, 0, true);  // coalesced into previous event
   SimulateWheelEvent(-30, -3, 0, true);  // 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::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+  // ScrollBegin, ScrollUpdate, and the second MouseWheel will be queued
+  // events.
   EXPECT_EQ(3U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::GestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_delegate()->current_mode());
+  // ScrollEnd will be the queued event.
+  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
 
   // Receive ACK for the second (coalesced) event as not processed. This will
   // start an overcroll gesture.
   SendInputEventACK(WebInputEvent::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
+  // ScrollBegin and ScrollUpdate will be queued events.
+  EXPECT_EQ(2U, GetSentMessageCountAndResetSink());
   SendInputEventACK(WebInputEvent::GestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   EXPECT_EQ(OVERSCROLL_WEST, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_WEST, overscroll_delegate()->current_mode());
-  EXPECT_EQ(0U, sink_->message_count());
+  // ScrollEnd will be the queued event.
+  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
 
   // Send a mouse-move event. This should cancel the overscroll navigation
   // (since the amount overscrolled is not above the threshold), and so the
   // mouse-move should reach the renderer.
   SimulateMouseMove(5, 10, 0);
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_delegate()->completed_mode());
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_delegate()->current_mode());
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
 
@@ skipping 52 matching lines @@
   SimulateWheelEvent(0, 10, 0, true);  // 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::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   SendInputEventACK(WebInputEvent::GestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_CONSUMED);
   EXPECT_TRUE(ScrollStateIsContentScrolling());
-  EXPECT_EQ(3U, GetSentMessageCountAndResetSink());
+  // ScrollBegin, ScrollUpdate, the second MouseWheel, and ScrollEnd will be
+  // queued events.
+  EXPECT_EQ(4U, GetSentMessageCountAndResetSink());
 
   // The second wheel event is consumed.
   SendInputEventACK(WebInputEvent::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   SendInputEventACK(WebInputEvent::GestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_CONSUMED);
   EXPECT_TRUE(ScrollStateIsContentScrolling());
+  // ScrollBegin, ScrollUpdate, and ScrollEnd will be queued events.
+  EXPECT_EQ(3U, sink_->message_count());
 
   // Touchpad scroll can end with a zero-velocity fling. But it is not
   // dispatched, but it should still reset the overscroll controller state.
   SimulateGestureEvent(WebInputEvent::GestureScrollBegin,
                        blink::WebGestureDeviceTouchscreen);
   SimulateGestureFlingStartEvent(0.f, 0.f, blink::WebGestureDeviceTouchpad);
   EXPECT_TRUE(ScrollStateIsUnknown());
-  EXPECT_EQ(3U, sink_->message_count());
+  // ScrollBegin, ScrollUpdate, ScrollEnd, and ScrollBegin will be queued
+  // events.
+  EXPECT_EQ(4U, 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());
 
   SimulateGestureEvent(WebInputEvent::GestureScrollEnd,
                        blink::WebGestureDeviceTouchscreen);
+  // ScrollBegin, ScrollUpdate, ScrollEnd, ScrollBegin, and ScrollEnd will be
+  // queued events.
+  EXPECT_EQ(5U, GetSentMessageCountAndResetSink());
 
   SimulateWheelEvent(-5, 0, 0, true);    // sent directly
   SimulateWheelEvent(-60, 0, 0, true);   // enqueued
   SimulateWheelEvent(-100, 0, 0, true);  // coalesced into previous event
   EXPECT_TRUE(ScrollStateIsUnknown());
-  EXPECT_EQ(5U, GetSentMessageCountAndResetSink());
+  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::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   SendInputEventACK(WebInputEvent::GestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   EXPECT_TRUE(ScrollStateIsUnknown());
-  EXPECT_EQ(3U, GetSentMessageCountAndResetSink());
+  // ScrollBegin, ScrollUpdate, the second Mousewheel, and ScrollEnd will be
+  // queued events.
+  EXPECT_EQ(4U, GetSentMessageCountAndResetSink());
 
   SendInputEventACK(WebInputEvent::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   SendInputEventACK(WebInputEvent::GestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   EXPECT_EQ(OVERSCROLL_WEST, overscroll_mode());
   EXPECT_TRUE(ScrollStateIsOverscrolling());
-  EXPECT_EQ(1U, sink_->message_count());
+  // ScrollBegin, ScrollUpdate, and ScrollEnd will be queued events.
+  EXPECT_EQ(3U, GetSentMessageCountAndResetSink());
 
   // The GestureScrollBegin will reset the delegate's mode, so check it here.
   EXPECT_EQ(OVERSCROLL_WEST, overscroll_delegate()->current_mode());
   SimulateGestureEvent(WebInputEvent::GestureScrollBegin,
                        blink::WebGestureDeviceTouchscreen);
   SimulateGestureFlingStartEvent(0.f, 0.f, blink::WebGestureDeviceTouchpad);
   EXPECT_EQ(OVERSCROLL_NONE, overscroll_mode());
   EXPECT_TRUE(ScrollStateIsUnknown());
-  EXPECT_EQ(3U, sink_->message_count());
+  // ScrollBegin will be the queued event.
+  EXPECT_EQ(1U, sink_->message_count());
   EXPECT_FALSE(parent_host_->input_router()->HasPendingEvents());
 }
 
 TEST_F(RenderWidgetHostViewAuraOverscrollTest, OverscrollResetsOnBlur) {
   SetUpOverscrollEnvironment();
 
   // Start an overscroll with gesture scroll. In the middle of the scroll, blur
   // the host.
   SimulateGestureEvent(WebInputEvent::GestureScrollBegin,
                        blink::WebGestureDeviceTouchscreen);
@@ skipping 839 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