Use scratch keys for stencil buffers.

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 205 matching lines @@
      * Called by CacheAccess.
      */
     void abandon();
 
     virtual size_t onGpuMemorySize() const = 0;
 
     // See comments in CacheAccess.
     bool setContentKey(const GrResourceKey& contentKey);
     void setBudgeted(bool countsAgainstBudget);
     void notifyIsPurgable() const;
+    void removeScratchKey();
 
 #ifdef SK_DEBUG
     friend class GrGpu; // for assert in GrGpu to access getGpu
 #endif
 
     static uint32_t CreateUniqueID();
 
     // We're in an internal doubly linked list owned by GrResourceCache2
     SK_DECLARE_INTERNAL_LLIST_INTERFACE(GrGpuResource);
 
@@ skipping 29 matching lines @@
     mutable size_t          fGpuMemorySize;
 
     uint32_t                fFlags;
     const uint32_t          fUniqueID;
 
     typedef GrIORef<GrGpuResource> INHERITED;
     friend class GrIORef<GrGpuResource>; // to access notifyIsPurgable.
 };
 
 #endif