add readPixels to SkImage

src/image/SkImage_Base.h

Index: src/image/SkImage_Base.h
diff --git a/src/image/SkImage_Base.h b/src/image/SkImage_Base.h
index 8f0fefe4f8622c110669c3f48fb60b557e522903..8c1dfada638db398c6b645c7e0c264c54a3b470c 100644
--- a/src/image/SkImage_Base.h
+++ b/src/image/SkImage_Base.h
@@ -41,13 +41,14 @@ public:
                                   const SkRect& dst, const SkPaint*) const = 0;
     virtual SkSurface* onNewSurface(const SkImageInfo&, const SkSurfaceProps&) const = 0;
 
-    // Default impl calls onDraw
-    virtual bool onReadPixels(SkBitmap*, const SkIRect& subset) const;
-
     virtual const void* onPeekPixels(SkImageInfo*, size_t* /*rowBytes*/) const {
         return NULL;
     }
 
+    // Default impl calls onDraw
+    virtual bool onReadPixels(const SkImageInfo& dstInfo, void* dstPixels, size_t dstRowBytes,
+                              int srcX, int srcY) const;
+    
     virtual GrTexture* onGetTexture() const { return NULL; }
 
     // return a read-only copy of the pixels. We promise to not modify them,