implement getBufferSubDataAsync prototype

gpu/command_buffer/client/gles2_implementation.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef GPU_COMMAND_BUFFER_CLIENT_GLES2_IMPLEMENTATION_H_
 #define GPU_COMMAND_BUFFER_CLIENT_GLES2_IMPLEMENTATION_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 228 matching lines @@
       GLenum pname, GLint* params);
   bool GetSyncivHelper(
       GLsync sync, GLenum pname, GLsizei bufsize, GLsizei* length,
       GLint* values);
   bool GetQueryObjectValueHelper(
       const char* function_name, GLuint id, GLenum pname, GLuint64* params);
 
   void FreeUnusedSharedMemory();
   void FreeEverything();
 
+  void FreeSharedMemory(void*) override;
+
   // ContextSupport implementation.
   void SignalSyncToken(const gpu::SyncToken& sync_token,
                        const base::Closure& callback) override;
   void SignalQuery(uint32_t query, const base::Closure& callback) override;
   void SetAggressivelyFreeResources(bool aggressively_free_resources) override;
 
   // base::trace_event::MemoryDumpProvider implementation.
   bool OnMemoryDump(const base::trace_event::MemoryDumpArgs& args,
                     base::trace_event::ProcessMemoryDump* pmd) override;
 
@@ skipping 613 matching lines @@
 
 inline bool GLES2Implementation::GetTexParameterivHelper(
     GLenum /* target */, GLenum /* pname */, GLint* /* params */) {
   return false;
 }
 
 }  // namespace gles2
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_CLIENT_GLES2_IMPLEMENTATION_H_