SkRectShaderImageFilter: add a new factory method which takes a CropRect.

include/effects/SkRectShaderImageFilter.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 SkRectShaderImageFilter_DEFINED
 #define SkRectShaderImageFilter_DEFINED
 
 #include "SkImageFilter.h"
 #include "SkRect.h"
 
 class SkShader;
 
 class SK_API SkRectShaderImageFilter : public SkImageFilter {
 public:
     /**
      *  The SkShader object will have its refcnt increased as it becomes a member of the
      *  SkRectShaderImageFilter object returned by this function. It cannot be NULL.
      *  The region parameter is used to specify on which region the shader is applied.

[reed1, 2013/10/14 12:45:57]

1. "region"?
2. It appears now that the rect/region is optional. Can you update the dox to
clarify what happens in that case?
3. Can you document what this filter does? e.g. why are we passing in a shader?

      */
     static SkRectShaderImageFilter* Create(SkShader* s, const SkRect& rect);
+    static SkRectShaderImageFilter* Create(SkShader* s, const CropRect* rect = NULL);
     virtual ~SkRectShaderImageFilter();
 
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkRectShaderImageFilter)
 
 protected:
     SkRectShaderImageFilter(SkFlattenableReadBuffer& buffer);
     virtual void flatten(SkFlattenableWriteBuffer&) const SK_OVERRIDE;
 
     virtual bool onFilterImage(Proxy*, const SkBitmap& src, const SkMatrix&,
                                SkBitmap* result, SkIPoint* loc) SK_OVERRIDE;
 
 private:
     SkRectShaderImageFilter(SkShader* s, const CropRect* rect);
     SkShader*  fShader;
 
     typedef SkImageFilter INHERITED;
 };
 
 #endif