Replace LayerImpl::sorting_context_id with transform reference.

cc/layers/layer_impl.h

 // 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.
 
 #ifndef CC_LAYERS_LAYER_IMPL_H_
 #define CC_LAYERS_LAYER_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 190 matching lines @@
   }
   SkBlendMode draw_blend_mode() const { return draw_blend_mode_; }
 
   void SetPosition(const gfx::PointF& position);
   gfx::PointF position() const { return position_; }
 
   bool IsAffectedByPageScale() const;
 
   gfx::Vector2dF FixedContainerSizeDelta() const;
 
-  bool Is3dSorted() const { return sorting_context_id_ != 0; }
+  bool Is3dSorted() const { return sorting_context_id() != 0; }
 
   void SetUseParentBackfaceVisibility(bool use) {
     use_parent_backface_visibility_ = use;
   }
   bool use_parent_backface_visibility() const {
     return use_parent_backface_visibility_;
   }
 
   void SetUseLocalTransformForBackfaceVisibility(bool use_local) {
     use_local_transform_for_backface_visibility_ = use_local;
@@ skipping 180 matching lines @@
     is_drawn_render_surface_layer_list_member_ = is_member;
   }
 
   bool is_drawn_render_surface_layer_list_member() const {
     return is_drawn_render_surface_layer_list_member_;
   }
 
   void set_may_contain_video(bool yes) { may_contain_video_ = yes; }
   bool may_contain_video() const { return may_contain_video_; }
 
-  void Set3dSortingContextId(int id);
-  int sorting_context_id() { return sorting_context_id_; }
+  // Layers that share a sorting context id will be sorted together in 3d
+  // space.  0 is a special value that means this layer will not be sorted and
+  // will be drawn in paint order.
+  int sorting_context_id() const;

[ajuma, 2017/01/06 14:59:55]

style nit: since this is no longer a trivial getter, it should be renamed
SortingContextId()

[wkorman, 2017/01/06 22:50:02]

Renamed to GetSortingContextId() (added Get prefix per conversation on
http://crrev.com/2611253003 with you and danakj@).

 
   // Get the correct invalidation region instead of conservative Rect
   // for layers that provide it.
   virtual Region GetInvalidationRegionForDebugging();
 
   virtual gfx::Rect GetEnclosingRectInTargetSpace() const;
 
   int num_copy_requests_in_target_subtree();
 
   void UpdatePropertyTreeForScrollingAndAnimationIfNeeded();
@@ skipping 107 matching lines @@
 
   gfx::Rect clip_rect_in_target_space_;
   int transform_tree_index_;
   int effect_tree_index_;
   int clip_tree_index_;
   int scroll_tree_index_;
 
  protected:
   friend class TreeSynchronizer;
 
-  // Layers that share a sorting context id will be sorted together in 3d
-  // space.  0 is a special value that means this layer will not be sorted and
-  // will be drawn in paint order.
-  int sorting_context_id_;
-
   DrawMode current_draw_mode_;
 
  private:
   ElementId element_id_;
   uint32_t mutable_properties_;
   // Rect indicating what was repainted/updated during update.
   // Note that plugin layers bypass this and leave it empty.
   // This is in the layer's space.
   gfx::Rect update_rect_;
 
@@ skipping 20 matching lines @@
   bool has_will_change_transform_hint_ : 1;
   bool needs_push_properties_ : 1;
   bool scrollbars_hidden_ : 1;
 
   DISALLOW_COPY_AND_ASSIGN(LayerImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_LAYER_IMPL_H_