Add sk_ref_sp helper function.

tests/RefCntTest.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkRefCnt.h"
 #include "SkThreadUtils.h"
 #include "SkTypes.h"
@@ skipping 367 matching lines @@
     sp.reset(rc);
     // We have transfered our ownership over to sp
     REPORTER_ASSERT(r, rc->unique());
 
     rc->ref();  // now "rc" is also an owner
     REPORTER_ASSERT(r, !rc->unique());
 
     sp.reset(rc);   // this should transfer our ownership over to sp
     REPORTER_ASSERT(r, rc->unique());
 }
+
+DEF_TEST(sk_sp_ref, r) {
+    SkRefCnt* rc = new SkRefCnt;
+    REPORTER_ASSERT(r, rc->unique());
+
+    {
+        sk_sp<SkRefCnt> sp = sk_ref_sp(rc);
+        REPORTER_ASSERT(r, !rc->unique());
+    }
+
+    REPORTER_ASSERT(r, rc->unique());
+    rc->unref();
+}