Add CompositingReasons to compositor layers.

cc/layers/layer.h

Index: cc/layers/layer.h
diff --git a/cc/layers/layer.h b/cc/layers/layer.h
index ee8cd027ceeb77c7a4940a01b65398ac718ca548..20d13ff95f36788c55d0fcca30181642bbc1f115 100644
--- a/cc/layers/layer.h
+++ b/cc/layers/layer.h
@@ -15,6 +15,7 @@
 #include "cc/base/cc_export.h"
 #include "cc/base/region.h"
 #include "cc/base/scoped_ptr_vector.h"
+#include "cc/layers/compositing_reasons.h"
 #include "cc/layers/draw_properties.h"
 #include "cc/layers/layer_lists.h"
 #include "cc/layers/layer_position_constraint.h"
@@ -284,6 +285,7 @@ class CC_EXPORT Layer : public base::RefCounted<Layer>,
   virtual void ReduceMemoryUsage() {}
 
   void SetDebugName(const std::string& debug_name);
+  void SetCompositingReasons(CompositingReasons reasons);
 
   virtual void PushPropertiesTo(LayerImpl* layer);
 
@@ -451,6 +453,7 @@ class CC_EXPORT Layer : public base::RefCounted<Layer>,
   gfx::PointF anchor_point_;
   SkColor background_color_;
   std::string debug_name_;
+  CompositingReasons compositing_reasons_;
   float opacity_;
   skia::RefPtr<SkImageFilter> filter_;
   WebKit::WebFilterOperations filters_;