Implement support for a Context parameter in image filters

include/effects/SkMagnifierImageFilter.h

 /*
  * Copyright 2012 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 SkMagnifierImageFilter_DEFINED
 #define SkMagnifierImageFilter_DEFINED
 
 #include "SkRect.h"
 #include "SkImageFilter.h"
 
 class SK_API SkMagnifierImageFilter : public SkImageFilter {
 public:
     static SkMagnifierImageFilter* Create(const SkRect& srcRect, SkScalar inset) {
         return SkNEW_ARGS(SkMagnifierImageFilter, (srcRect, inset));
     }
 
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkMagnifierImageFilter)
 
 protected:
     explicit SkMagnifierImageFilter(SkReadBuffer& buffer);
     virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE;
 
-    virtual bool onFilterImage(Proxy*, const SkBitmap& src, const SkMatrix&,
+    virtual bool onFilterImage(Proxy*, const SkBitmap& src, const Context&,
                                SkBitmap* result, SkIPoint* offset) const SK_OVERRIDE;
 #if SK_SUPPORT_GPU
     virtual bool asNewEffect(GrEffectRef** effect, GrTexture* texture, const SkMatrix& matrix, const SkIRect& bounds) const SK_OVERRIDE;
 #endif
 
 #ifdef SK_SUPPORT_LEGACY_PUBLICEFFECTCONSTRUCTORS
 public:
 #endif
     SkMagnifierImageFilter(const SkRect& srcRect, SkScalar inset);
 
 private:
     SkRect fSrcRect;
     SkScalar fInset;
     typedef SkImageFilter INHERITED;
 };
 
 #endif