MouseWheelEventQueue sends scrollEnd right away when latching is disabled.

content/browser/renderer_host/input/input_router_impl_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/input_router_impl.h"
 
 #include <math.h>
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 1008 matching lines @@
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
 
   // Indicate that the wheel event was unhandled.
   SendInputEventACK(WebInputEvent::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
 
   // Check that the ack for the MouseWheel and ScrollBegin
   // were processed.
   EXPECT_EQ(2U, ack_handler_->GetAndResetAckCount());
 
-  // There should be a ScrollBegin and ScrollUpdate, MouseWheel sent
+  // There should be a ScrollBegin and ScrollUpdate, MouseWheel sent.
   EXPECT_EQ(3U, GetSentMessageCountAndResetSink());
 
   EXPECT_EQ(ack_handler_->acked_wheel_event().deltaY, -5);
   SendInputEventACK(WebInputEvent::GestureScrollUpdate,
                     INPUT_EVENT_ACK_STATE_CONSUMED);
+
+  // There should be a ScrollEnd sent.

[dtapuska, 2017/03/29 17:49:03]

Can we adjust this comment so it indicates the GestureScrollEnd is released from
the queue?

[sahel, 2017/03/29 20:10:43]

Done.

+  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
+
+  // Check that the ack for the ScrollUpdate and ScrollEnd
+  // were processed.
+  EXPECT_EQ(2U, ack_handler_->GetAndResetAckCount());
+
   SendInputEventACK(WebInputEvent::MouseWheel,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
 
+  // There should be a ScrollBegin and ScrollUpdate sent.
+  EXPECT_EQ(2U, GetSentMessageCountAndResetSink());
+
   // Check that the correct unhandled wheel event was received.
   EXPECT_EQ(2U, ack_handler_->GetAndResetAckCount());
-  EXPECT_EQ(INPUT_EVENT_ACK_STATE_NOT_CONSUMED, ack_handler_->ack_state());
+  EXPECT_EQ(INPUT_EVENT_ACK_STATE_NOT_CONSUMED,
+            ack_handler_->acked_wheel_event_state());
   EXPECT_EQ(ack_handler_->acked_wheel_event().deltaY, -10);
+
+  SendInputEventACK(WebInputEvent::GestureScrollUpdate,
+                    INPUT_EVENT_ACK_STATE_CONSUMED);
+
+  // There should be a ScrollEnd sent.

[dtapuska, 2017/03/29 17:49:03]

Same.. the event is already "sent" from the mouse_wheel_event_queue not just
from the gesture event queue.

[sahel, 2017/03/29 20:10:43]

Done.

+  EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
+
+  // Check that the ack for the ScrollUpdate and ScrollEnd
+  // were processed.
+  EXPECT_EQ(2U, ack_handler_->GetAndResetAckCount());
 }
 
 TEST_F(InputRouterImplTest, TouchTypesIgnoringAck) {
   OnHasTouchEventHandlers(true);
   // Only acks for TouchCancel should always be ignored.
   ASSERT_TRUE(
       ShouldBlockEventStream(GetEventWithType(WebInputEvent::TouchStart)));
   ASSERT_TRUE(
       ShouldBlockEventStream(GetEventWithType(WebInputEvent::TouchMove)));
   ASSERT_TRUE(
@@ skipping 1398 matching lines @@
   EXPECT_EQ(80, sent_event->data.flingStart.velocityY);
 
   const WebGestureEvent* filter_event =
       GetFilterWebInputEvent<WebGestureEvent>();
   TestLocationInFilterEvent(filter_event, orig);
   EXPECT_EQ(30, filter_event->data.flingStart.velocityX);
   EXPECT_EQ(40, filter_event->data.flingStart.velocityY);
 }
 
 }  // namespace content