Make SkBlurImageFilter capable of cropping during blur (GPU path).

src/effects/SkBlurMaskFilter.cpp

Index: src/effects/SkBlurMaskFilter.cpp
diff --git a/src/effects/SkBlurMaskFilter.cpp b/src/effects/SkBlurMaskFilter.cpp
index 5b5a4a033fc8324835594e4ed114036df3344616..13c7d45a0e049338587c0686f7ca1a30c0a250a6 100644
--- a/src/effects/SkBlurMaskFilter.cpp
+++ b/src/effects/SkBlurMaskFilter.cpp
@@ -1236,7 +1236,7 @@ bool SkBlurMaskFilterImpl::filterMaskGPU(GrTexture* src,
     // gaussianBlur.  Otherwise, we need to save it for later compositing.
     bool isNormalBlur = (kNormal_SkBlurStyle == fBlurStyle);
     *result = SkGpuBlurUtils::GaussianBlur(context, src, isNormalBlur && canOverwriteSrc,
-                                           clipRect, false, xformedSigma, xformedSigma,
+                                           clipRect, nullptr, xformedSigma, xformedSigma,
                                            GrTextureProvider::kApprox_SizeConstraint);
     if (nullptr == *result) {
         return false;