SkBlurImageFilter returns input when sigma = 0

include/effects/SkBlurImageFilter.h

 /*
  * Copyright 2011 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkBlurImageFilter_DEFINED
 #define SkBlurImageFilter_DEFINED
 
 #include "SkImageFilter.h"
 #include "SkSize.h"
 
 class SK_API SkBlurImageFilter : public SkImageFilter {
 public:
     static SkImageFilter* Create(SkScalar sigmaX, SkScalar sigmaY, SkImageFilter* input = NULL,
                                  const CropRect* cropRect = NULL) {
+        if (0 == sigmaX && 0 == sigmaY && nullptr == cropRect) {
+            return SkSafeRef(input);
+        }
         return new SkBlurImageFilter(sigmaX, sigmaY, input, cropRect);
     }
 
     void computeFastBounds(const SkRect&, SkRect*) const override;
 
     SK_TO_STRING_OVERRIDE()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkBlurImageFilter)
 
 protected:
     void flatten(SkWriteBuffer&) const override;
     bool onFilterImage(Proxy*, const SkBitmap& src, const Context&, SkBitmap* result,
                        SkIPoint* offset) const override;
     void onFilterNodeBounds(const SkIRect& src, const SkMatrix&,
                             SkIRect* dst, MapDirection) const override;
     bool canFilterImageGPU() const override { return true; }
     bool filterImageGPU(Proxy* proxy, const SkBitmap& src, const Context& ctx, SkBitmap* result,
                         SkIPoint* offset) const override;
 
 private:
     SkBlurImageFilter(SkScalar sigmaX,
                       SkScalar sigmaY,
                       SkImageFilter* input,
                       const CropRect* cropRect);
 
     SkSize   fSigma;
     typedef SkImageFilter INHERITED;
 };
 
 #endif