Force use of and cache render surface.

cc/layers/layer.h

Index: cc/layers/layer.h
diff --git a/cc/layers/layer.h b/cc/layers/layer.h
index c88721b0fa6e1e82ad3728900e1d3f93b7cc566b..37eb6039fb99fe9bdcdebabeed602c576caaaf5d 100644
--- a/cc/layers/layer.h
+++ b/cc/layers/layer.h
@@ -249,10 +249,8 @@ class CC_EXPORT Layer : public base::RefCounted<Layer> {
     inputs_.did_scroll_callback = callback;
   }
 
-  void SetForceRenderSurfaceForTesting(bool force_render_surface);
-  bool force_render_surface_for_testing() const {
-    return force_render_surface_for_testing_;
-  }
+  void SetForceRenderSurface(bool force_render_surface);

[weiliangc, 2017/06/07 21:19:00]

Preferably a different name to distinguish old force_render_surface_for_testing_
behavior with current behavior. Since force_render_surface_for_testing_ doesn't
has same assumption about reuse.

Also add a comment saying what ui's force_render_surface does.

[wutao, 2017/06/09 02:31:32]

As discussed offline, will call the API cache_render_surface for now. There is a
comment in the ui::Layer.

+  bool force_render_surface() const { return force_render_surface_; }
 
   gfx::ScrollOffset CurrentScrollOffset() const {
     return inputs_.scroll_offset;
@@ -615,7 +613,7 @@ class CC_EXPORT Layer : public base::RefCounted<Layer> {
   bool draws_content_ : 1;
   bool use_local_transform_for_backface_visibility_ : 1;
   bool should_check_backface_visibility_ : 1;
-  bool force_render_surface_for_testing_ : 1;
+  bool force_render_surface_ : 1;
   bool subtree_property_changed_ : 1;
   bool may_contain_video_ : 1;
   bool is_scroll_clip_layer_ : 1;