Create blurred RRect mask on GPU (rather than uploading it)

src/effects/SkGpuBlurUtils.h

Index: src/effects/SkGpuBlurUtils.h
diff --git a/src/effects/SkGpuBlurUtils.h b/src/effects/SkGpuBlurUtils.h
index a5de6a242ac86bce661de0ba42b54d56d8c87b22..a12a08873c3a4c8bac439a9b97120fd1d0546388 100644
--- a/src/effects/SkGpuBlurUtils.h
+++ b/src/effects/SkGpuBlurUtils.h
@@ -29,6 +29,7 @@ namespace SkGpuBlurUtils {
     *                        no pixels will be sampled outside of this rectangle.
     * @param sigmaX          The blur's standard deviation in X.
     * @param sigmaY          The blur's standard deviation in Y.
+    * @param fit             backing fit for the returned draw context
     * @return                The drawContext containing the blurred result.
     */
     sk_sp<GrDrawContext> GaussianBlur(GrContext* context,
@@ -37,7 +38,8 @@ namespace SkGpuBlurUtils {
                                       const SkIRect& dstBounds,
                                       const SkIRect* srcBounds,
                                       float sigmaX,
-                                      float sigmaY);
+                                      float sigmaY,
+                                      SkBackingFit fit = SkBackingFit::kApprox);
 };
 
 #endif