Add CompositingReasons to compositor layers.

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 64aeccb1bc90a14879f730fcf9762adf573ce60f..0bf84806d136fabf32fd49cad7887cc1a195ba3c 100644
--- a/cc/layers/layer_impl.h
+++ b/cc/layers/layer_impl.h
@@ -16,6 +16,7 @@
 #include "cc/base/region.h"
 #include "cc/base/scoped_ptr_vector.h"
 #include "cc/input/input_handler.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"
@@ -200,6 +201,14 @@ class CC_EXPORT LayerImpl : LayerAnimationValueObserver {
   void SetDebugName(const std::string& debug_name) { debug_name_ = debug_name; }
   std::string debug_name() const { return debug_name_; }
 
+  void SetCompositingReasons(CompositingReasons reasons) {
+      compositing_reasons_ = reasons;
+  }
+
+  CompositingReasons compositing_reasons() const {
+      return compositing_reasons_;
+  }
+
   bool ShowDebugBorders() const;
 
   // These invalidate the host's render surface layer list.  The caller
@@ -515,6 +524,7 @@ class CC_EXPORT LayerImpl : LayerAnimationValueObserver {
 
   // Debug layer name.
   std::string debug_name_;
+  CompositingReasons compositing_reasons_;
 
   WebKit::WebFilterOperations filters_;
   WebKit::WebFilterOperations background_filters_;