Force use of and cache render surface.

cc/layers/layer_impl.h

Index: cc/layers/layer_impl.h
diff --git a/cc/layers/layer_impl.h b/cc/layers/layer_impl.h
index 87891ce1b8d1c62a2a0b27d601d64f26dd413040..92e0aebb8dedd8f0a5441fdd52e12e215583852e 100644
--- a/cc/layers/layer_impl.h
+++ b/cc/layers/layer_impl.h
@@ -344,6 +344,7 @@ class CC_EXPORT LayerImpl {
   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();