cc: Clean up root_layer code in LTI

cc/trees/layer_tree_impl.h

 // 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.
 
 #ifndef CC_TREES_LAYER_TREE_IMPL_H_
 #define CC_TREES_LAYER_TREE_IMPL_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 113 matching lines @@
   void SetNeedsRedraw();
 
   // Tracing methods.
   // ---------------------------------------------------------------------------
   void GetAllPrioritizedTilesForTracing(
       std::vector<PrioritizedTile>* prioritized_tiles) const;
   void AsValueInto(base::trace_event::TracedValue* dict) const;
 
   // Other public methods
   // ---------------------------------------------------------------------------
-  LayerImpl* root_layer() const { return root_layer_; }
+  LayerImpl* root_layer_for_testing() {
+    return layer_list_.empty() ? nullptr : layer_list_[0];
+  }
   RenderSurfaceImpl* RootRenderSurface() const;
   bool LayerListIsEmpty() const;
-  void SetRootLayer(std::unique_ptr<LayerImpl>);
-  void SetRootLayerFromLayerList();
+  void SetRootLayerForTesting(std::unique_ptr<LayerImpl>);
+  void SetRootLayerFromLayerListForTesting();
+  void OnCanDrawStateChangedForTree();
   bool IsRootLayer(const LayerImpl* layer) const;
   std::unique_ptr<OwnedLayerImplList> DetachLayers();
 
   void SetPropertyTrees(PropertyTrees* property_trees);
   PropertyTrees* property_trees() { return &property_trees_; }
 
   void UpdatePropertyTreesForBoundsDelta();
 
   void PushPropertiesTo(LayerTreeImpl* tree_impl);
 
@@ skipping 344 matching lines @@
                                 float max_page_scale_factor);
   bool IsViewportLayerId(int id) const;
   void UpdateScrollbars(int scroll_layer_id, int clip_layer_id);
   void DidUpdatePageScale();
   void PushTopControls(const float* top_controls_shown_ratio);
   bool ClampTopControlsShownRatio();
 
   LayerTreeHostImpl* layer_tree_host_impl_;
   int source_frame_number_;
   int is_first_frame_after_commit_tracker_;
-  LayerImpl* root_layer_;
+  LayerImpl* root_layer_for_testing_;
   HeadsUpDisplayLayerImpl* hud_layer_;
   PropertyTrees property_trees_;
   SkColor background_color_;
   bool has_transparent_background_;
 
   int last_scrolled_layer_id_;
   int overscroll_elasticity_layer_id_;
   int page_scale_layer_id_;
   int inner_viewport_scroll_layer_id_;
   int outer_viewport_scroll_layer_id_;
@@ skipping 71 matching lines @@
 
   std::unique_ptr<PendingPageScaleAnimation> pending_page_scale_animation_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(LayerTreeImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_IMPL_H_