Add SkCachedData and use it for SkMipMap

src/core/SkResourceCache.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkResourceCache_DEFINED
 #define SkResourceCache_DEFINED
 
 #include "SkBitmap.h"
 
+class SkCachedData;
 class SkDiscardableMemory;
 class SkMipMap;
 
 /**
  *  Cache object for bitmaps (with possible scale in X Y as part of the key).
  *
  *  Multiple caches can be instantiated, but each instance is not implicitly
  *  thread-safe, so if a given instance is to be shared across threads, the
  *  caller must manage the access itself (e.g. via a mutex).
  *
@@ skipping 167 matching lines @@
      */
     size_t setTotalByteLimit(size_t newLimit);
 
     void purgeAll() {
         this->purgeAsNeeded(true);
     }
 
     DiscardableFactory discardableFactory() const { return fDiscardableFactory; }
     SkBitmap::Allocator* allocator() const { return fAllocator; };
 
+    SkCachedData* newCachedData(size_t bytes);
+
     /**
      *  Call SkDebugf() with diagnostic information about the state of the cache
      */
     void dump() const;
 
 private:
     Rec*    fHead;
     Rec*    fTail;
 
     class Hash;
@@ skipping 18 matching lines @@
 
     void init();    // called by constructors
 
 #ifdef SK_DEBUG
     void validate() const;
 #else
     void validate() const {}
 #endif
 };
 #endif