Implement srcRect and dstRect functionality in SkBitmapSource. This is required for the "preserveAs…

include/effects/SkBitmapSource.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 SkBitmapSource_DEFINED
 #define SkBitmapSource_DEFINED
 
 #include "SkImageFilter.h"
 #include "SkBitmap.h"
 
 class SK_API SkBitmapSource : public SkImageFilter {
 public:
     explicit SkBitmapSource(const SkBitmap& bitmap);
+    SkBitmapSource(const SkBitmap& bitmap, const SkRect& srcRect, const SkRect& dstRect);
 
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkBitmapSource)
 
 protected:
     explicit SkBitmapSource(SkFlattenableReadBuffer& buffer);
     virtual void flatten(SkFlattenableWriteBuffer&) const SK_OVERRIDE;
     virtual bool onFilterImage(Proxy*, const SkBitmap& src, const SkMatrix&,
                                SkBitmap* result, SkIPoint* offset) SK_OVERRIDE;
 
 private:
     SkBitmap fBitmap;
+    SkRect   fSrcRect, fDstRect;
     typedef SkImageFilter INHERITED;
 };
 
 #endif