private iterator to visit all resource cache entries

src/core/SkCachedData.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkCachedData_DEFINED
 #define SkCachedData_DEFINED
 
@@ skipping 12 matching lines @@
 
     void* writable_data() { return fData; }
 
     void ref() const { this->internalRef(false); }
     void unref() const { this->internalUnref(false); }
 
     int testing_only_getRefCnt() const { return fRefCnt; }
     bool testing_only_isLocked() const { return fIsLocked; }
     bool testing_only_isInCache() const { return fInCache; }
 
+    SkDiscardableMemory* diagnostic_only_getDiscardable() const {
+        return kDiscardableMemory_StorageType == fStorageType ? fStorage.fDM : nullptr;
+    }
+
 protected:
     // called when fData changes. could be NULL.
     virtual void onDataChange(void* oldData, void* newData) {}
 
 private:
     SkMutex fMutex;     // could use a pool of these...
 
     enum StorageType {
         kDiscardableMemory_StorageType,
         kMalloc_StorageType
@@ skipping 55 matching lines @@
     void attachToCacheAndRef() const { this->internalRef(true); }
 
     /*
      *  Call when removing this instance from a SkResourceCache::Rec subclass
      *  (typically in the Rec's destructor).
      */
     void detachFromCacheAndUnref() const { this->internalUnref(true); }
 };
 
 #endif