Reimplement gpu message bus for invalidated bitmap gen IDs

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 246 matching lines @@
 private:
     /**
      * Frees the object in the underlying 3D API. Called by CacheAccess.
      */
     void release();
 
     virtual size_t onGpuMemorySize() const = 0;
 
     // See comments in CacheAccess.
     bool setContentKey(const GrContentKey& contentKey);
+    void removeContentKey();
     void notifyIsPurgeable() const;
     void removeScratchKey();
     void makeBudgeted();
     void makeUnbudgeted();
 
 #ifdef SK_DEBUG
     friend class GrGpu; // for assert in GrGpu to access getGpu
 #endif
 
     static uint32_t CreateUniqueID();
@@ skipping 14 matching lines @@
     LifeCycle                   fLifeCycle;
     const uint32_t              fUniqueID;
 
     SkAutoTUnref<const SkData>  fData;
 
     typedef GrIORef<GrGpuResource> INHERITED;
     friend class GrIORef<GrGpuResource>; // to access notifyIsPurgeable.
 };
 
 #endif