Notify Blink about start of gesture scroll through a queued event.

content/browser/renderer_host/input/touch_event_queue_unittest.cc

 // Copyright 2013 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/input/touch_event_queue.h"
 
 #include <stddef.h>
 #include <utility>
 
 #include "base/location.h"
@@ skipping 217 matching lines @@
   void ReleaseTouchPoint(int index) {
     touch_event_.ReleasePoint(index);
     SendTouchEvent();
   }
 
   void CancelTouchPoint(int index) {
     touch_event_.CancelPoint(index);
     SendTouchEvent();
   }
 
+  void PrependTouchScrollNotification() {
+    queue_->PrependTouchScrollNotification();
+  }
+
   void AdvanceTouchTime(double seconds) {
     touch_event_.timeStampSeconds += seconds;
   }
 
   void ResetTouchEvent() {
     touch_event_ = SyntheticWebTouchEvent();
   }
 
   size_t GetAndResetAckedEventCount() {
     size_t count = acked_event_count_;
@@ skipping 2362 matching lines @@
 
   // TouchMove should be allowed and test for touches state.
   const WebTouchEvent& event2 = sent_event();
   EXPECT_EQ(WebInputEvent::TouchMove, event2.type);
   EXPECT_EQ(WebTouchPoint::StateStationary, event2.touches[0].state);
   EXPECT_EQ(WebTouchPoint::StateMoved, event2.touches[1].state);
   EXPECT_EQ(1U, GetAndResetSentEventCount());
   EXPECT_EQ(1U, GetAndResetAckedEventCount());
 }
 
+// Tests that touch-scroll-notification event is placed at the correct position
+// in the queue.
+TEST_F(TouchEventQueueTest, TouchScrollNotificationOrder) {

[tdresser, 2016/04/01 14:50:24]

Aren't there a few cases we should test?
1. Queue is empty when we receive the notification.
2. Queue has length one.
3. Queue has length > 1 (probably test with > 3)

Perhaps we don't need #2, but I suspect at least 1 and 3 should be tested.

[mustaq, 2016/04/01 18:31:05]

Added all, including #2 where the notification is at the end of the queue.

+  PressTouchPoint(1, 1);
+  MoveTouchPoint(0, 5, 5);
+  ReleaseTouchPoint(0);
+
+  EXPECT_EQ(0U, GetAndResetAckedEventCount());
+  EXPECT_EQ(3U, queued_event_count());
+
+  // Send the touch-scroll-notification when 3 events are in the queue.
+  PrependTouchScrollNotification();
+
+  EXPECT_EQ(0U, GetAndResetAckedEventCount());
+  EXPECT_EQ(4U, queued_event_count());
+
+  // Receive an ACK for the touchstart.
+  SendTouchEventAck(INPUT_EVENT_ACK_STATE_CONSUMED);
+
+  EXPECT_EQ(1U, GetAndResetAckedEventCount());
+  EXPECT_EQ(WebInputEvent::TouchStart, acked_event().type);
+  EXPECT_EQ(3U, queued_event_count());
+
+  // Receive an ACK for the touch-scroll-notification.
+  SendTouchEventAck(INPUT_EVENT_ACK_STATE_IGNORED);
+
+  EXPECT_EQ(0U, GetAndResetAckedEventCount());
+  EXPECT_EQ(2U, queued_event_count());
+
+  // Receive an ACK for the touchmove.
+  SendTouchEventAck(INPUT_EVENT_ACK_STATE_CONSUMED);
+
+  EXPECT_EQ(1U, GetAndResetAckedEventCount());
+  EXPECT_EQ(WebInputEvent::TouchMove, acked_event().type);
+  EXPECT_EQ(1U, queued_event_count());
+
+  // Receive an ACK for the touchend.
+  SendTouchEventAck(INPUT_EVENT_ACK_STATE_CONSUMED);
+
+  EXPECT_EQ(1U, GetAndResetAckedEventCount());
+  EXPECT_EQ(WebInputEvent::TouchEnd, acked_event().type);
+  EXPECT_EQ(0U, queued_event_count());
+
+  EXPECT_EQ(4U, all_sent_events().size());
+  EXPECT_EQ(WebInputEvent::TouchStart, all_sent_events()[0].type);
+  EXPECT_EQ(WebInputEvent::TouchScrollStarted, all_sent_events()[1].type);
+  EXPECT_EQ(WebInputEvent::TouchMove, all_sent_events()[2].type);
+  EXPECT_EQ(WebInputEvent::TouchEnd, all_sent_events()[3].type);
+}
+
 }  // namespace content