Implement correct clipping for image filters.

include/effects/SkDisplacementMapEffect.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 SkDisplacementMapEffect_DEFINED
 #define SkDisplacementMapEffect_DEFINED
 
@@ skipping 21 matching lines @@
 
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkDisplacementMapEffect)
 
     virtual bool onFilterImage(Proxy* proxy,
                                const SkBitmap& src,
                                const SkMatrix& ctm,
                                SkBitmap* dst,
                                SkIPoint* offset) SK_OVERRIDE;
     virtual void computeFastBounds(const SkRect& src, SkRect* dst) const SK_OVERRIDE;
 
+    virtual bool onFilterBounds(const SkIRect& src, const SkMatrix&,
+                                SkIRect* dst) const SK_OVERRIDE;
+
 #if SK_SUPPORT_GPU
     virtual bool canFilterImageGPU() const SK_OVERRIDE { return true; }
     virtual bool filterImageGPU(Proxy* proxy, const SkBitmap& src, const SkMatrix& ctm,
                                 SkBitmap* result, SkIPoint* offset) SK_OVERRIDE;
 #endif
 
 protected:
     explicit SkDisplacementMapEffect(SkReadBuffer& buffer);
     virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE;
 
 private:
     ChannelSelectorType fXChannelSelector;
     ChannelSelectorType fYChannelSelector;
     SkScalar fScale;
     typedef SkImageFilter INHERITED;
     SkImageFilter* getDisplacementInput() { return getInput(0); }
     SkImageFilter* getColorInput() { return getInput(1); }
     const SkImageFilter* getDisplacementInput() const { return getInput(0); }
     const SkImageFilter* getColorInput() const { return getInput(1); }
 };
 
 #endif