Revert of Moving SkBlurImageFilter into core

src/core/SkGpuBlurUtils.h

Index: src/core/SkGpuBlurUtils.h
diff --git a/src/core/SkGpuBlurUtils.h b/src/core/SkGpuBlurUtils.h
deleted file mode 100644
index a12a08873c3a4c8bac439a9b97120fd1d0546388..0000000000000000000000000000000000000000
--- a/src/core/SkGpuBlurUtils.h
+++ /dev/null
@@ -1,46 +0,0 @@
-/*
- * 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 "GrDrawContext.h"
-
-class GrContext;
-class GrTexture;
-
-struct SkRect;
-
-namespace SkGpuBlurUtils {
-  /**
-    * 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 colorSpace      Color space of the source (used for the drawContext result, too).
-    * @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.
-    * @param fit             backing fit for the returned draw context
-    * @return                The drawContext containing the blurred result.
-    */
-    sk_sp<GrDrawContext> GaussianBlur(GrContext* context,
-                                      GrTexture* srcTexture,
-                                      sk_sp<SkColorSpace> colorSpace,
-                                      const SkIRect& dstBounds,
-                                      const SkIRect* srcBounds,
-                                      float sigmaX,
-                                      float sigmaY,
-                                      SkBackingFit fit = SkBackingFit::kApprox);
-};
-
-#endif
-#endif