have reset() return its argument as a convenience

git-svn-id: http://skia.googlecode.com/svn/trunk@8141 2bbb7eff-a529-9590-31e7-b0007b416f81

include/core/SkRefCnt.h

@@ -164,9 +164,10 @@ public:
 
     T* get() const { return fObj; }
 
-    void reset(T* obj) {
+    T* reset(T* obj) {
         SkSafeUnref(fObj);
         fObj = obj;
+        return obj;
     }
 
     void swap(SkAutoTUnref* other) {