Record scroll_layer_id instead of scrollbar_animation_controller pointer

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 204 matching lines @@
       content_is_suitable_for_gpu_rasterization_(true),
       has_gpu_rasterization_trigger_(false),
       use_gpu_rasterization_(false),
       use_msaa_(false),
       gpu_rasterization_status_(GpuRasterizationStatus::OFF_DEVICE),
       input_handler_client_(NULL),
       did_lock_scrolling_layer_(false),
       wheel_scrolling_(false),
       scroll_affects_scroll_handler_(false),
       scroll_layer_id_mouse_currently_over_(Layer::INVALID_ID),
+      scroll_layer_id_mouse_currently_captured_(Layer::INVALID_ID),
       tile_priorities_dirty_(false),
       settings_(settings),
       visible_(false),
       cached_managed_memory_policy_(settings.gpu_memory_policy),
       is_synchronous_single_threaded_(!task_runner_provider->HasImplThread() &&
                                       !settings.single_thread_proxy_scheduler),
       // Must be initialized after is_synchronous_single_threaded_ and
       // task_runner_provider_.
       tile_manager_(this,
                     GetTaskRunner(),
                     std::move(image_worker_task_runner),
                     is_synchronous_single_threaded_
                         ? std::numeric_limits<size_t>::max()
                         : settings.scheduled_raster_task_limit,
                     settings.ToTileManagerSettings()),
       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 2999 matching lines @@
 
   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) {
     animation_controller->DidMouseDown();
-    captured_scrollbar_animation_controller_ = animation_controller;
+    scroll_layer_id_mouse_currently_captured_ =
+        scroll_layer_id_mouse_currently_over_;
   }
 }
 
 void LayerTreeHostImpl::MouseUp() {
-  if (captured_scrollbar_animation_controller_) {
-    captured_scrollbar_animation_controller_->DidMouseUp();
-    captured_scrollbar_animation_controller_ = nullptr;
+  if (scroll_layer_id_mouse_currently_captured_ != Layer::INVALID_ID) {
+    ScrollbarAnimationController* animation_controller =
+        ScrollbarAnimationControllerForId(
+            scroll_layer_id_mouse_currently_captured_);
+
+    scroll_layer_id_mouse_currently_captured_ = Layer::INVALID_ID;
+
+    if (animation_controller)
+      animation_controller->DidMouseUp();
   }
 }
 
 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.
@@ skipping 829 matching lines @@
       worker_context_visibility_ =
           worker_context->CacheController()->ClientBecameVisible();
     } else {
       worker_context->CacheController()->ClientBecameNotVisible(
           std::move(worker_context_visibility_));
     }
   }
 }
 
 }  // namespace cc