Add a 'unique' method to SkRefCnt, document the usage, and add support.

src/core/SkTypefaceCache.cpp

 
 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 
@@ skipping 51 matching lines @@
     }
     return NULL;
 }
 
 void SkTypefaceCache::purge(int numToPurge) {
     int count = fArray.count();
     int i = 0;
     while (i < count) {
         SkTypeface* face = fArray[i].fFace;
         bool strong = fArray[i].fStrong;
-        if ((strong && face->getRefCnt() == 1) ||
-            (!strong && face->weak_expired()))
-        {
+        if ((strong && face->unique()) || (!strong && face->weak_expired())) {
             if (strong) {
                 face->unref();
             } else {
                 face->weak_unref();
             }
             fArray.remove(i);
             --count;
             if (--numToPurge == 0) {
                 return;
             }
@@ skipping 53 matching lines @@
     return false;
 }
 #endif
 
 void SkTypefaceCache::Dump() {
 #ifdef SK_DEBUG
     SkAutoMutexAcquire ama(gMutex);
     (void)Get().findByProcAndRef(DumpProc, NULL);
 #endif
 }