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

src/effects/SkGpuBlurUtils.cpp

Index: src/effects/SkGpuBlurUtils.cpp
diff --git a/src/effects/SkGpuBlurUtils.cpp b/src/effects/SkGpuBlurUtils.cpp
index 869cd76c5b7e74a0a9c2a74b6ec7b0353ebe7502..ebb480d3dfb5e8d89d1f0f96c3c80ad99f85dad0 100644
--- a/src/effects/SkGpuBlurUtils.cpp
+++ b/src/effects/SkGpuBlurUtils.cpp
@@ -186,7 +186,8 @@ sk_sp<GrDrawContext> GaussianBlur(GrContext* context,
                                   const SkIRect& dstBounds,
                                   const SkIRect* srcBounds,
                                   float sigmaX,
-                                  float sigmaY) {
+                                  float sigmaY,
+                                  SkBackingFit fit) {
     SkASSERT(context);
     SkIRect clearRect;
     int scaleFactorX, radiusX;
@@ -226,7 +227,7 @@ sk_sp<GrDrawContext> GaussianBlur(GrContext* context,
     const int height = dstBounds.height();
     const GrPixelConfig config = srcTexture->config();
 
-    sk_sp<GrDrawContext> dstDrawContext(context->makeDrawContext(SkBackingFit::kApprox,
+    sk_sp<GrDrawContext> dstDrawContext(context->makeDrawContext(fit,
                                                                  width, height, config, colorSpace,
                                                                  0, kDefault_GrSurfaceOrigin));
     if (!dstDrawContext) {
@@ -246,7 +247,7 @@ sk_sp<GrDrawContext> GaussianBlur(GrContext* context,
         return dstDrawContext;
     } 
 
-    sk_sp<GrDrawContext> tmpDrawContext(context->makeDrawContext(SkBackingFit::kApprox,
+    sk_sp<GrDrawContext> tmpDrawContext(context->makeDrawContext(fit,
                                                                  width, height, config, colorSpace,
                                                                  0, kDefault_GrSurfaceOrigin));
     if (!tmpDrawContext) {