add peekPixels to SkCanvas and SkSurface

include/core/SkSurface.h

Index: include/core/SkSurface.h
diff --git a/include/core/SkSurface.h b/include/core/SkSurface.h
index 2f277b755df7a9d385f57e812d6a2e97c2d9af72..74c5f083f459bb9f48fd195bccef609562fa3859 100644
--- a/include/core/SkSurface.h
+++ b/include/core/SkSurface.h
@@ -151,6 +151,18 @@ public:
      */
     void draw(SkCanvas*, SkScalar x, SkScalar y, const SkPaint*);
 
+    /**
+     *  If the surface has direct access to its pixels (i.e. they are in local
+     *  RAM) return the const-address of those pixels, and if not null, return
+     *  the ImageInfo and rowBytes. The returned address is only valid while
+     *  the surface object is in scope, and no API call is made on the surface
+     *  or its canvas.
+     *
+     *  On failure, returns NULL and the info and rowBytes parameters are
+     *  ignored.
+     */
+    const void* peekPixels(SkImageInfo* info, size_t* rowBytes);
+
 protected:
     SkSurface(int width, int height);
     SkSurface(const SkImageInfo&);