change all interfaces for SkRasterizer to const, in preparation for marking it
as immutable/re-entrant safe.
Review URL: https://codereview.appspot.com/6936064

git-svn-id: http://skia.googlecode.com/svn/trunk@6878 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/include/effects/SkLayerRasterizer.h b/include/effects/SkLayerRasterizer.h
index 7a1ef74..65d1be0 100644
--- a/include/effects/SkLayerRasterizer.h
+++ b/include/effects/SkLayerRasterizer.h
@@ -41,7 +41,7 @@
     // override from SkRasterizer
     virtual bool onRasterize(const SkPath& path, const SkMatrix& matrix,
                              const SkIRect* clipBounds,
-                             SkMask* mask, SkMask::CreateMode mode);
+                             SkMask* mask, SkMask::CreateMode mode) const;
 
 private:
     SkDeque fLayers;