Implement crop rect for SkImageFilter

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
 
 #if SK_SUPPORT_GPU
 class GrTexture;
 class GrContext;
 #endif
 
 struct SkRect;
 
 namespace SkGpuBlurUtils {
 
 #if SK_SUPPORT_GPU
   /**
     * Applies a 2D Gaussian blur to a given texture.
     * @param context         The GPU context
     * @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 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
     * new texture.  It is the caller's responsibility to unref this texture.
     */
     GrTexture* GaussianBlur(GrContext* context,
                             GrTexture* srcTexture,
                             bool canClobberSrc,
                             const SkRect& rect,
+                            bool cropToRect,
                             float sigmaX,
                             float sigmaY);
 #endif
 
 };
 
 #endif