Refactor LayerTreeImpl's scrollbar map to be keyed on element ids

cc/input/single_scrollbar_animation_controller_thinning_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 "cc/input/single_scrollbar_animation_controller_thinning.h"
 
 #include "cc/layers/solid_color_scrollbar_layer_impl.h"
 #include "cc/test/fake_impl_task_runner_provider.h"
 #include "cc/test/fake_layer_tree_host_impl.h"
 #include "cc/test/geometry_test_utils.h"
@@ skipping 17 matching lines @@
         kDefaultMouseMoveDistanceToTriggerAnimation;
 
 class MockSingleScrollbarAnimationControllerClient
     : public ScrollbarAnimationControllerClient {
  public:
   explicit MockSingleScrollbarAnimationControllerClient(
       LayerTreeHostImpl* host_impl)
       : host_impl_(host_impl) {}
   virtual ~MockSingleScrollbarAnimationControllerClient() {}
 
-  ScrollbarSet ScrollbarsFor(int scroll_layer_id) const override {
-    return host_impl_->ScrollbarsFor(scroll_layer_id);
+  ScrollbarSet ScrollbarsFor(ElementId scroll_element_id) const override {
+    return host_impl_->ScrollbarsFor(scroll_element_id);
   }
 
   MOCK_METHOD2(PostDelayedScrollbarAnimationTask,
                void(const base::Closure& start_fade, base::TimeDelta delay));
   MOCK_METHOD0(SetNeedsRedrawForScrollbarAnimation, void());
   MOCK_METHOD0(SetNeedsAnimateForScrollbarAnimation, void());
   MOCK_METHOD0(DidChangeScrollbarVisibility, void());
   MOCK_METHOD0(start_fade, base::Closure());
   MOCK_METHOD0(delay, base::TimeDelta());
 
  private:
   LayerTreeHostImpl* host_impl_;
 };
 
 class SingleScrollbarAnimationControllerThinningTest : public testing::Test {
  public:
   SingleScrollbarAnimationControllerThinningTest()
       : host_impl_(&task_runner_provider_, &task_graph_runner_),
         client_(&host_impl_) {}
 
  protected:
   const base::TimeDelta kThinningDuration = base::TimeDelta::FromSeconds(2);
 
   void SetUp() override {
     std::unique_ptr<LayerImpl> scroll_layer =
         LayerImpl::Create(host_impl_.active_tree(), 1);
     std::unique_ptr<LayerImpl> clip =
         LayerImpl::Create(host_impl_.active_tree(), 3);
+    scroll_layer->SetElementId(
+        LayerIdToElementIdForTesting(scroll_layer->id()));
     clip_layer_ = clip.get();
     scroll_layer->SetScrollClipLayer(clip_layer_->id());
     LayerImpl* scroll_layer_ptr = scroll_layer.get();
 
     const int kId = 2;
     const int kThumbThickness = 10;
     const int kTrackStart = 0;
     const bool kIsLeftSideVerticalScrollbar = false;
     const bool kIsOverlayScrollbar = true;
 
     std::unique_ptr<SolidColorScrollbarLayerImpl> scrollbar =
         SolidColorScrollbarLayerImpl::Create(
             host_impl_.active_tree(), kId, HORIZONTAL, kThumbThickness,
             kTrackStart, kIsLeftSideVerticalScrollbar, kIsOverlayScrollbar);
     scrollbar_layer_ = scrollbar.get();
 
     scroll_layer->test_properties()->AddChild(std::move(scrollbar));
     clip_layer_->test_properties()->AddChild(std::move(scroll_layer));
     host_impl_.active_tree()->SetRootLayerForTesting(std::move(clip));
 
     scrollbar_layer_->SetScrollInfo(scroll_layer_ptr->id(),
                                     scroll_layer_ptr->element_id());
     scrollbar_layer_->test_properties()->opacity_can_animate = true;
     clip_layer_->SetBounds(gfx::Size(100, 100));
     scroll_layer_ptr->SetBounds(gfx::Size(200, 200));
     host_impl_.active_tree()->BuildLayerListAndPropertyTreesForTesting();
 
     scrollbar_controller_ = SingleScrollbarAnimationControllerThinning::Create(
-        scroll_layer_ptr->id(), HORIZONTAL, &client_, kThinningDuration);
+        scroll_layer_ptr->element_id(), HORIZONTAL, &client_,
+        kThinningDuration);

[wkorman, 2017/04/19 18:07:09]

I think I dreamed that I knew what a thinning scroll bar was the other night.

   }
 
   FakeImplTaskRunnerProvider task_runner_provider_;
   TestTaskGraphRunner task_graph_runner_;
   FakeLayerTreeHostImpl host_impl_;
   std::unique_ptr<SingleScrollbarAnimationControllerThinning>
       scrollbar_controller_;
   LayerImpl* clip_layer_;
   SolidColorScrollbarLayerImpl* scrollbar_layer_;
   NiceMock<MockSingleScrollbarAnimationControllerClient> client_;
@@ skipping 267 matching lines @@
                   scrollbar_layer_->thumb_thickness_scale_factor());
 
   time += kThinningDuration / 2;
   scrollbar_controller_->Animate(time);
   EXPECT_FLOAT_EQ(kIdleThicknessScale,
                   scrollbar_layer_->thumb_thickness_scale_factor());
 }
 
 }  // namespace
 }  // namespace cc