Add support for clipstack to Gr. GrClip is now a list of rects and paths with set operations to combine them. The stencil buffer is used to perform the set operations to put the clip into the stencil buffer. Building Gr's clip from Skia's clipStack is currently disabled due to the fact that Skia's clipStack is relative to the root layer not the current layer. This will be fixed in a subsequent CL.

git-svn-id: http://skia.googlecode.com/svn/trunk@878 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/include/gpu/SkGpuDevice.h b/include/gpu/SkGpuDevice.h
index 2db3380..3fed99a 100644
--- a/include/gpu/SkGpuDevice.h
+++ b/include/gpu/SkGpuDevice.h
@@ -68,7 +68,8 @@
      *  Override from SkGpuDevice, so we can set our FBO to be the render target
      *  The canvas parameter must be a SkGpuCanvas
      */
-    virtual void gainFocus(SkCanvas*, const SkMatrix&, const SkRegion&);
+    virtual void gainFocus(SkCanvas*, const SkMatrix&, const SkRegion&,
+                           const SkClipStack& clipStack);
 
     virtual SkGpuTexture* accessTexture() { return (SkGpuTexture*)fTexture; }