cc: Distinguish single texture mask from normal masks

cc/layers/picture_layer.h

Index: cc/layers/picture_layer.h
diff --git a/cc/layers/picture_layer.h b/cc/layers/picture_layer.h
index f4e2751404104b1c10af954fea6d5bf0d430c472..80be77c300a6ab7171f601aeb7b77efa10062d43 100644
--- a/cc/layers/picture_layer.h
+++ b/cc/layers/picture_layer.h
@@ -35,6 +35,7 @@ class CC_EXPORT PictureLayer : public Layer {
   void SetNeedsDisplayRect(const gfx::Rect& layer_rect) override;
   bool Update() override;
   void SetIsMask(bool is_mask) override;
+  void SetIsSingleTextureMask(bool is_single_texture_mask) override;
   sk_sp<SkPicture> GetPicture() const override;
 
   bool IsSuitableForGpuRasterization() const override;
@@ -71,6 +72,7 @@ class CC_EXPORT PictureLayer : public Layer {
   bool HasDrawableContent() const override;
 
   bool is_mask() const { return is_mask_; }
+  bool is_single_texture_mask() const { return is_single_texture_mask_; }
 
   PictureLayerInputs picture_layer_inputs_;
 
@@ -87,6 +89,7 @@ class CC_EXPORT PictureLayer : public Layer {
 
   int update_source_frame_number_;
   bool is_mask_;
+  bool is_single_texture_mask_;
 
   DISALLOW_COPY_AND_ASSIGN(PictureLayer);
 };