Replace layer id with Element id for tracking scrollbar animation controllers

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 67 matching lines @@
     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_->SetScrollLayerId(scroll_layer_ptr->id());
+    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);
   }
 
   FakeImplTaskRunnerProvider task_runner_provider_;
@@ skipping 274 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