cc: nine patch: add occlusion support

cc/layers/nine_patch_layer.h

Index: cc/layers/nine_patch_layer.h
diff --git a/cc/layers/nine_patch_layer.h b/cc/layers/nine_patch_layer.h
index 20b5e4934149f3fffc1343ca15626e49cf75c6bd..ab57c129b227fbc0bf356c8c47ef46db1426c534 100644
--- a/cc/layers/nine_patch_layer.h
+++ b/cc/layers/nine_patch_layer.h
@@ -41,6 +41,11 @@ class CC_EXPORT NinePatchLayer : public UIResourceLayer {
   void SetFillCenter(bool fill_center);
   void SetNearestNeighbor(bool nearest_neighbor);
 
+  // |rect| is the space completely occluded by another layer in layer
+  // space. This can be used for example to occlude the entire window's
+  // content when drawing the shadow with a 9 patches layer.
+  void SetLayerOcclusion(const gfx::Rect& rect);

[aelias_OOO_until_Jul13, 2016/04/20 05:54:57]

nit: call the variable "occlusion", not "rect".

[llandwerlin-old, 2016/04/21 09:53:14]

Done.

+
  private:
   NinePatchLayer();
   ~NinePatchLayer() override;
@@ -54,6 +59,9 @@ class CC_EXPORT NinePatchLayer : public UIResourceLayer {
   // image space.
   gfx::Rect image_aperture_;
 
+  // The occluded region in layer space set by SetLayerOcclusion.

[aelias_OOO_until_Jul13, 2016/04/20 05:54:57]

Would it be accurate to write "May be larger than the image aperture"?  If so,
please add that comment.

[llandwerlin-old, 2016/04/21 09:53:14]

Done.

+  gfx::Rect layer_occlusion_;
+
   DISALLOW_COPY_AND_ASSIGN(NinePatchLayer);
 };