Implement drawDRRect for GPU

BUG=skia:2259
R=jvanverth@google.com

Author: bsalomon@google.com

Review URL: https://codereview.chromium.org/220233011

git-svn-id: http://skia.googlecode.com/svn/trunk@14118 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/include/gpu/SkGpuDevice.h b/include/gpu/SkGpuDevice.h
index d7d797a..a823191 100644
--- a/include/gpu/SkGpuDevice.h
+++ b/include/gpu/SkGpuDevice.h
@@ -91,6 +91,8 @@
                           const SkPaint& paint) SK_OVERRIDE;
     virtual void drawRRect(const SkDraw&, const SkRRect& r,
                            const SkPaint& paint) SK_OVERRIDE;
+    virtual void drawDRRect(const SkDraw& draw, const SkRRect& outer,
+                            const SkRRect& inner, const SkPaint& paint) SK_OVERRIDE;
     virtual void drawOval(const SkDraw&, const SkRect& oval,
                           const SkPaint& paint) SK_OVERRIDE;
     virtual void drawPath(const SkDraw&, const SkPath& path,