Pass MouseUp to the captured scrollbar animation controller in layer tree

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 229 matching lines @@
                     settings.check_tile_priority_inversion),
       pinch_gesture_active_(false),
       pinch_gesture_end_should_clear_scrolling_layer_(false),
       fps_counter_(
           FrameRateCounter::Create(task_runner_provider_->HasImplThread())),
       memory_history_(MemoryHistory::Create()),
       debug_rect_history_(DebugRectHistory::Create()),
       max_memory_needed_bytes_(0),
       resourceless_software_draw_(false),
       mutator_host_(std::move(mutator_host)),
+      captured_scrollbar_animation_controller_(nullptr),
       rendering_stats_instrumentation_(rendering_stats_instrumentation),
       micro_benchmark_controller_(this),
       task_graph_runner_(task_graph_runner),
       id_(id),
       requires_high_res_to_draw_(false),
       is_likely_to_require_a_draw_(false),
       has_valid_compositor_frame_sink_(false),
       mutator_(nullptr) {
   DCHECK(mutator_host_);
   mutator_host_->SetMutatorHostClient(this);
@@ skipping 2968 matching lines @@
   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 =
       ScrollbarAnimationControllerForId(scroll_layer_id_mouse_currently_over_);
-  if (animation_controller)
+  if (animation_controller) {
     animation_controller->DidMouseDown();
+    captured_scrollbar_animation_controller_ = animation_controller;
+  }
 }
 
 void LayerTreeHostImpl::MouseUp() {
-  ScrollbarAnimationController* animation_controller =
-      ScrollbarAnimationControllerForId(scroll_layer_id_mouse_currently_over_);
-  if (animation_controller)
-    animation_controller->DidMouseUp();
+  if (captured_scrollbar_animation_controller_) {
+    captured_scrollbar_animation_controller_->DidMouseUp();
+    captured_scrollbar_animation_controller_ = nullptr;
+  }
 }
 
 void LayerTreeHostImpl::MouseMoveAt(const gfx::Point& viewport_point) {
   gfx::PointF device_viewport_point = gfx::ScalePoint(
       gfx::PointF(viewport_point), active_tree_->device_scale_factor());
   LayerImpl* layer_impl =
       active_tree_->FindLayerThatIsHitByPoint(device_viewport_point);
 
   // Check if mouse is over a scrollbar or not.
   // TODO(sahel): get rid of this extera checking when
@@ skipping 828 matching lines @@
       worker_context_visibility_ =
           worker_context->CacheController()->ClientBecameVisible();
     } else {
       worker_context->CacheController()->ClientBecameNotVisible(
           std::move(worker_context_visibility_));
     }
   }
 }
 
 }  // namespace cc