Overlay scrollbars expand only when mouse is near thumb

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 3369 matching lines @@
   if (!CurrentlyScrollingNode()) {
     scroll_status.thread = SCROLL_IGNORED;
     scroll_status.main_thread_scrolling_reasons =
         MainThreadScrollingReason::kNoScrollingLayer;
   } else {
     scroll_status.thread = SCROLL_ON_IMPL_THREAD;
   }
   return scroll_status;
 }
 
-float LayerTreeHostImpl::DeviceSpaceDistanceToLayer(
-    const gfx::PointF& device_viewport_point,
-    LayerImpl* layer_impl) {
-  if (!layer_impl)
-    return std::numeric_limits<float>::max();
-
-  gfx::Rect layer_impl_bounds(layer_impl->bounds());
-
-  gfx::RectF device_viewport_layer_impl_bounds = MathUtil::MapClippedRect(
-      layer_impl->ScreenSpaceTransform(), gfx::RectF(layer_impl_bounds));
-
-  return device_viewport_layer_impl_bounds.ManhattanDistanceToPoint(
-      device_viewport_point);
-}
-
 void LayerTreeHostImpl::MouseDown() {
   ScrollbarAnimationController* animation_controller =
       ScrollbarAnimationControllerForElementId(
           scroll_element_id_mouse_currently_over_);
   if (animation_controller) {
     animation_controller->DidMouseDown();
     scroll_element_id_mouse_currently_captured_ =
         scroll_element_id_mouse_currently_over_;
   }
 }
@@ skipping 48 matching lines @@
     }
     scroll_element_id_mouse_currently_over_ = scroll_element_id;
   }
 
   ScrollbarAnimationController* new_animation_controller =
       ScrollbarAnimationControllerForElementId(scroll_element_id);
   if (!new_animation_controller)
     return;
 
   for (auto* scrollbar : active_tree_->ScrollbarsFor(scroll_element_id)) {
-    new_animation_controller->DidMouseMoveNear(
-        scrollbar->orientation(),
-        DeviceSpaceDistanceToLayer(device_viewport_point, scrollbar) /
-            active_tree_->device_scale_factor());
+    new_animation_controller->DidMouseMoveNear(scrollbar->orientation(),
+                                               device_viewport_point);
   }
 }
 
 void LayerTreeHostImpl::MouseLeave() {
   for (auto& pair : scrollbar_animation_controllers_)
     pair.second->DidMouseLeave();
   scroll_element_id_mouse_currently_over_ = ElementId();
 }
 
 void LayerTreeHostImpl::PinchGestureBegin() {
@@ skipping 809 matching lines @@
 }
 
 void LayerTreeHostImpl::UpdateScrollSourceInfo(bool is_wheel_scroll) {
   if (is_wheel_scroll)
     has_scrolled_by_wheel_ = true;
   else
     has_scrolled_by_touch_ = true;
 }
 
 }  // namespace cc