Implement crop rect for lighting image filters.

include/core/SkImageFilter.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkImageFilter_DEFINED
 #define SkImageFilter_DEFINED
 
@@ skipping 73 matching lines @@
     /**
      *  Returns true if the filter can be expressed a single-pass
      *  GrEffect, used to process this filter on the GPU, or false if
      *  not.
      *
      *  If effect is non-NULL, a new GrEffect instance is stored
      *  in it.  The caller assumes ownership of the stage, and it is up to the
      *  caller to unref it.
      *
      *  The effect can assume its vertexCoords space maps 1-to-1 with texels
-     *  in the texture.
+     *  in the texture.  "offset" is the delta between the source and
+     *  destination rect's origins, when cropped processing is being performed.
      */
-    virtual bool asNewEffect(GrEffectRef** effect, GrTexture*) const;
+    virtual bool asNewEffect(GrEffectRef** effect, GrTexture*, const SkIPoint& offset) const;
 
     /**
      *  Returns true if the filter can be processed on the GPU.  This is most
      *  often used for multi-pass effects, where intermediate results must be
      *  rendered to textures.  For single-pass effects, use asNewEffect().
      *  The default implementation returns asNewEffect(NULL, NULL).
      */
     virtual bool canFilterImageGPU() const;
 
     /**
@@ skipping 69 matching lines @@
     bool applyCropRect(SkIRect* rect) const;
 
 private:
     typedef SkFlattenable INHERITED;
     int fInputCount;
     SkImageFilter** fInputs;
     SkIRect fCropRect;
 };
 
 #endif