Fix cc scrollbar layer issues with initialization, and use element ids throughout.

cc/layers/scrollbar_layer_unittest.cc

 // Copyright 2012 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 <stddef.h>
 
 #include <unordered_map>
 
 #include "base/memory/ptr_util.h"
 #include "base/threading/thread_task_runner_handle.h"
@@ skipping 625 matching lines @@
 
 TEST_F(ScrollbarLayerTest, ScrollbarLayerOpacity) {
   const int kThumbThickness = 3;
   const int kTrackStart = 0;
 
   std::unique_ptr<Scrollbar> scrollbar(new FakeScrollbar(false, true, true));
 
   scoped_refptr<Layer> layer_tree_root = Layer::Create();
   scoped_refptr<Layer> scroll_layer = Layer::Create();
   scroll_layer->SetScrollClipLayerId(layer_tree_root->id());
+  scroll_layer->SetElementId(ElementId(200));
   scoped_refptr<Layer> child1 = Layer::Create();
-  scoped_refptr<Layer> scrollbar_layer;
+  scoped_refptr<SolidColorScrollbarLayer> scrollbar_layer;
   const bool kIsLeftSideVerticalScrollbar = false;
   scrollbar_layer = SolidColorScrollbarLayer::Create(
       scrollbar->Orientation(), kThumbThickness, kTrackStart,
       kIsLeftSideVerticalScrollbar, scroll_layer->element_id());
+  scrollbar_layer->SetElementId(ElementId(300));
   scroll_layer->AddChild(child1);
   scroll_layer->InsertChild(scrollbar_layer, 1);
   layer_tree_root->AddChild(scroll_layer);
   layer_tree_host_->SetRootLayer(layer_tree_root);
+  scrollbar_layer->SetScrollElementId(scroll_layer->element_id());
 
   // Choose layer bounds to give max_scroll_offset = (8, 8).
   layer_tree_root->SetBounds(gfx::Size(2, 2));
   scroll_layer->SetBounds(gfx::Size(10, 10));
 
   // Building property trees twice shouldn't change the size of
   // PropertyTrees::always_use_active_tree_opacity_effect_ids.
   layer_tree_host_->BuildPropertyTreesForTesting();
-  EXPECT_EQ(layer_tree_host_->property_trees()
-                ->always_use_active_tree_opacity_effect_ids.size(),
-            1u);
   layer_tree_host_->property_trees()->needs_rebuild = true;
   layer_tree_host_->BuildPropertyTreesForTesting();
-  EXPECT_EQ(layer_tree_host_->property_trees()
-                ->always_use_active_tree_opacity_effect_ids.size(),
-            1u);
 
   // A solid color scrollbar layer's opacity is initialized to 0 on main thread
   layer_tree_host_->UpdateLayers();
   EffectNode* node = layer_tree_host_->property_trees()->effect_tree.Node(
       scrollbar_layer->effect_tree_index());
   EXPECT_EQ(node->opacity, 0.f);
 
   // This tests that the initial opacity(0) of the scrollbar gets pushed onto
   // the pending tree and then onto the active tree.
   LayerTreeHostImpl* host_impl = layer_tree_host_->host_impl();
@@ skipping 588 matching lines @@
   TestScale(gfx::Rect(1240, 0, 15, 1333), 2.7754839f);
   TestScale(gfx::Rect(1240, 0, 15, 677), 2.46677136f);
 
   // Horizontal Scrollbars.
   TestScale(gfx::Rect(0, 1240, 1333, 15), 2.7754839f);
   TestScale(gfx::Rect(0, 1240, 677, 15), 2.46677136f);
 }
 
 }  // namespace
 }  // namespace cc