Retract GrRenderTarget a bit within SkGpuDevice

include/gpu/GrDrawContext.h

Index: include/gpu/GrDrawContext.h
diff --git a/include/gpu/GrDrawContext.h b/include/gpu/GrDrawContext.h
index 04b03d4b6087bb06526c780252d732d3796dc81c..1ffa987f8a39569e03392101320c562049111a24 100644
--- a/include/gpu/GrDrawContext.h
+++ b/include/gpu/GrDrawContext.h
@@ -258,6 +258,7 @@ public:
      */
     void drawBatch(const GrClip&, const GrPaint&, GrDrawBatch*);
 
+    const GrSurfaceDesc& desc() const { return fRenderTarget->desc(); }
     int width() const { return fRenderTarget->width(); }
     int height() const { return fRenderTarget->height(); }
     int numColorSamples() const { return fRenderTarget->numColorSamples(); }