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

src/effects/SkGpuBlurUtils.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkGpuBlurUtils_DEFINED
 #define SkGpuBlurUtils_DEFINED
 
@@ skipping 11 matching lines @@
     * as a drawContext in case the caller wishes to future draw into the result.
     * Note: one of sigmaX and sigmaY should be non-zero!
     * @param context         The GPU context
     * @param srcTexture      The source texture to be blurred.
     * @param colorSpace      Color space of the source (used for the drawContext result, too).
     * @param dstBounds       The destination bounds, relative to the source texture.
     * @param srcBounds       The source bounds, relative to the source texture. If non-null,
     *                        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,
                                       GrTexture* srcTexture,
                                       sk_sp<SkColorSpace> colorSpace,
                                       const SkIRect& dstBounds,
                                       const SkIRect* srcBounds,
                                       float sigmaX,
-                                      float sigmaY);
+                                      float sigmaY,
+                                      SkBackingFit fit = SkBackingFit::kApprox);
 };
 
 #endif
 #endif