Revert of Moving SkBlurImageFilter into core

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 "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