Change implementation of flush-count based GrGpuResource purging

include/gpu/GrGpuResource.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 GrGpuResource_DEFINED
 #define GrGpuResource_DEFINED
 
@@ skipping 269 matching lines @@
 
 #ifdef SK_DEBUG
     friend class GrGpu; // for assert in GrGpu to access getGpu
 #endif
     // An index into a heap when this resource is purgeable or an array when not. This is maintained
     // by the cache.
     int                         fCacheArrayIndex;
     // This value reflects how recently this resource was accessed in the cache. This is maintained
     // by the cache.
     uint32_t                    fTimestamp;
+    uint32_t                    fExternalFlushCntWhenBecamePurgeable;
 
     static const size_t kInvalidGpuMemorySize = ~static_cast<size_t>(0);
     GrScratchKey                fScratchKey;
     GrUniqueKey                 fUniqueKey;
 
     // This is not ref'ed but abandon() or release() will be called before the GrGpu object
     // is destroyed. Those calls set will this to NULL.
     GrGpu*                      fGpu;
     mutable size_t              fGpuMemorySize;
 
     SkBudgeted                  fBudgeted;
     bool                        fRefsWrappedObjects;
     const uint32_t              fUniqueID;
 
     typedef GrIORef<GrGpuResource> INHERITED;
     friend class GrIORef<GrGpuResource>; // to access notifyAllCntsAreZero and notifyRefCntIsZero.
 };
 
 #endif