Build property trees for the HUD layer when using layer lists

cc/layers/layer.h

 // Copyright 2010 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_H_
 #define CC_LAYERS_LAYER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 28 matching lines @@
 
 namespace base {
 namespace trace_event {
 class ConvertableToTraceFormat;
 }
 }
 
 namespace cc {
 
 class CopyOutputRequest;
+class HeadsUpDisplayLayer;
 class LayerClient;
 class LayerImpl;
 class LayerTreeHost;
 class LayerTreeHostCommon;
 class LayerTreeImpl;
 class MutatorHost;
 class ScrollbarLayerInterface;
 
 // Base class for composited layers. Special layer types are derived from
 // this class.
@@ skipping 371 matching lines @@
   ElementListType GetElementTypeForAnimation() const;
 
   void SetScrollbarsHiddenFromImplSide(bool hidden);
 
   void set_is_scroll_clip_layer() { is_scroll_clip_layer_ = true; }
 
   const gfx::Rect& update_rect() const { return inputs_.update_rect; }
 
   LayerTreeHost* layer_tree_host() const { return layer_tree_host_; }
 
+  void copyPropertyTreeStateTo(HeadsUpDisplayLayer* hud_layer) const;

[ajuma, 2017/03/23 17:41:27]

not-blink-nit: Upper-case c :)

At a higher level, since we only need this for the specific case of copying root
layer state to the hud layer, I wonder if this would be better off as a helper
that did just that in LayerTreeHost rather than here.

Alternatively, if this seems like something we might want more generally, then
this should take a Layer* instead of a HeadsUpDisplayLayer*.

+
  protected:
   friend class LayerImpl;
   friend class TreeSynchronizer;
   virtual ~Layer();
   Layer();
 
   // These SetNeeds functions are in order of severity of update:
   //
   // Called when a property has been modified in a way that the layer knows
   // immediately that a commit is required.  This implies SetNeedsPushProperties
@@ skipping 198 matching lines @@
   // These all act like draw properties, so don't need push properties.
   gfx::Rect visible_layer_rect_;
   size_t num_unclipped_descendants_;
 
   DISALLOW_COPY_AND_ASSIGN(Layer);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_LAYER_H_