Force use of and cache render surface.

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 326 matching lines @@
   // Note this rect is in layer space (not content space).
   void SetUpdateRect(const gfx::Rect& update_rect);
   const gfx::Rect& update_rect() const { return update_rect_; }
 
   void AddDamageRect(const gfx::Rect& damage_rect);
   const gfx::Rect& damage_rect() const { return damage_rect_; }
 
   virtual std::unique_ptr<base::DictionaryValue> LayerTreeAsJson();
 
   bool LayerPropertyChanged() const;
+  bool LayerPropertyChangedOnly() const;

[vmpstr, 2017/07/13 18:01:02]

This looks a bit awkward. Maybe LayerPropertyChanged should be renamed to
something else first?

My concern is that LayerPropertyChanged vs LayerPropertyChangedOnly looks like
it would return the same value. 

Maybe LayerPropertyChanged should be something like LayerNeedsUpdate or
LayerIsDamaged. I think it depends on where we use it, but these two functions
definitely need to be named more distinctly.

Also, could you add comments to both of them; maybe writing the comment would
help come up with a better name.

[wutao, 2017/07/14 00:02:53]

I am a little worry that there are 45 references to LayerPropertyChanged().
Rename it will make even more changes to this patch. I could do it in separate
cl though.

I would like to add comments and rename my new function, such as
LayerPropertyChangedNotFromPropertyTrees() for now?

 
   void ResetChangeTracking();
 
   virtual SimpleEnclosedRegion VisibleOpaqueRegion() const;
 
   virtual void DidBecomeActive() {}
 
   virtual void DidBeginTracing();
 
   // Release resources held by this layer. Called when the output surface
@@ skipping 207 matching lines @@
   bool raster_even_if_not_drawn_ : 1;
 
   bool has_transform_node_ : 1;
 
   DISALLOW_COPY_AND_ASSIGN(LayerImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_LAYER_IMPL_H_