Address warnings from clang build bot

http://codereview.appspot.com/6506111/



git-svn-id: http://skia.googlecode.com/svn/trunk@5518 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/animator/SkDrawGradient.h b/src/animator/SkDrawGradient.h
index d01ee70..d7fc694 100644
--- a/src/animator/SkDrawGradient.h
+++ b/src/animator/SkDrawGradient.h
@@ -20,7 +20,7 @@
     DECLARE_PRIVATE_MEMBER_INFO(DrawGradient);
     SkDrawGradient();
     virtual ~SkDrawGradient();
-    virtual bool add(SkAnimateMaker& , SkDisplayable* child);
+    virtual bool add(SkAnimateMaker& , SkDisplayable* child) SK_OVERRIDE;
 #ifdef SK_DUMP_ENABLED
     virtual void dumpRest(SkAnimateMaker*);
 #endif