cancel overlay-scrollbar hover state when moving pointer out of window for ChromeOS

cc/trees/layer_tree_host_impl.cc

 // Copyright 2011 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 "cc/trees/layer_tree_host_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 3248 matching lines @@
   for (ScrollbarLayerImplBase* scrollbar :
        ScrollbarsFor(scroll_layer_impl->id()))
     distance_to_scrollbar =
         std::min(distance_to_scrollbar,
                  DeviceSpaceDistanceToLayer(device_viewport_point, scrollbar));
 
   animation_controller->DidMouseMoveNear(distance_to_scrollbar /
                                          active_tree_->device_scale_factor());
 }
 
+void LayerTreeHostImpl::MouseLeave() {
+  ScrollbarAnimationController* animation_controller =

[bokan, 2016/10/04 20:57:41]

What if the mouse isn't over the scrollbar though, rather near it when the mouse
leaves the window. This can happen if the mouse moves really quickly or if
there's a DIV whose scrollbars are showing. (DIVs do work, but only if they're
composited. To test, try running with the
--enable-prefer-compositing-to-lcd-text flag, that should enable animated
scrollbars on most DIVs and IFrames.

[chaopeng, 2016/10/05 02:29:29]

Yes, It doesnot work for near-moveout. I add a new patch for this. PTAL. Thank
you.

+      ScrollbarAnimationControllerForId(
+        scroll_layer_id_when_mouse_over_scrollbar_);
+
+  if (animation_controller) {

[dtapuska, 2016/10/04 20:50:22]

don't think you need the scope brackets :-)

+    animation_controller->DidMouseLeave();
+  }
+}
+
 void LayerTreeHostImpl::HandleMouseOverScrollbar(LayerImpl* layer_impl) {
   int new_id = Layer::INVALID_ID;
   if (layer_impl && layer_impl->ToScrollbarLayer())
     new_id = layer_impl->ToScrollbarLayer()->ScrollLayerId();
 
   if (new_id == scroll_layer_id_when_mouse_over_scrollbar_)
     return;
 
   ScrollbarAnimationController* old_animation_controller =
       ScrollbarAnimationControllerForId(
@@ skipping 886 matching lines @@
   if (is_visible) {
     worker_context_visibility_ =
         worker_context->CacheController()->ClientBecameVisible();
   } else {
     worker_context->CacheController()->ClientBecameNotVisible(
         std::move(worker_context_visibility_));
   }
 }
 
 }  // namespace cc