Make SkGpuBlurUtils::GaussianBlur more drawContext centric

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
-#include "GrTextureProvider.h"
+#include "GrDrawContext.h"
 
+class GrContext;
 class GrTexture;
-class GrContext;
-#endif
 
 struct SkRect;
 
 namespace SkGpuBlurUtils {
-
-#if SK_SUPPORT_GPU
   /**
-    * Applies a 2D Gaussian blur to a given texture.
+    * Applies a 2D Gaussian blur to a given texture. The blurred result is returned
+    * 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 gammaCorrect    Should blur be gamma-correct (sRGB to linear, etc...)
     * @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
-    * new texture.  It is the caller's responsibility to unref this texture.
+    * @return                The drawContext containing the blurred result.
     */
-    GrTexture* GaussianBlur(GrContext* context,
-                            GrTexture* srcTexture,
-                            bool gammaCorrect,
-                            const SkRect& dstBounds,
-                            const SkRect* srcBounds,
-                            float sigmaX,
-                            float sigmaY);
-#endif
+    sk_sp<GrDrawContext> GaussianBlur(GrContext* context,
+                                      GrTexture* srcTexture,
+                                      bool gammaCorrect,
+                                      const SkRect& dstBounds,
+                                      const SkRect* srcBounds,
+                                      float sigmaX,
+                                      float sigmaY);
 
 };
 
 #endif
+#endif