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

src/effects/SkGpuBlurUtils.h

Index: src/effects/SkGpuBlurUtils.h
diff --git a/src/effects/SkGpuBlurUtils.h b/src/effects/SkGpuBlurUtils.h
index 357a0d729ca2146cc859a8516f277caeb5b50af9..84e3252cc2a4dd9df286eeb59d3d449f2b119f98 100644
--- a/src/effects/SkGpuBlurUtils.h
+++ b/src/effects/SkGpuBlurUtils.h
@@ -26,9 +26,9 @@ namespace SkGpuBlurUtils {
     * @param srcTexture      The source texture to be blurred.
     * @param canClobberSrc   If true, srcTexture may be overwritten, and
     *                        may be returned as the result.
-    * @param rect            The destination rectangle.
-    * @param cropToRect      If true, do not sample any pixels outside the
-    *                        source rect.
+    * @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.
     * @return the blurred texture, which may be srcTexture reffed, or a
@@ -37,8 +37,8 @@ namespace SkGpuBlurUtils {
     GrTexture* GaussianBlur(GrContext* context,
                             GrTexture* srcTexture,
                             bool canClobberSrc,
-                            const SkRect& rect,
-                            bool cropToRect,
+                            const SkRect& dstBounds,
+                            const SkRect* srcBounds,
                             float sigmaX,
                             float sigmaY,
                             GrTextureProvider::SizeConstraint);