gpu: Reuse existing code for shared memory allocation.

base/memory/shared_memory.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 BASE_MEMORY_SHARED_MEMORY_H_
 #define BASE_MEMORY_SHARED_MEMORY_H_
 
 #include <stddef.h>
 
 #include <string>
@@ skipping 174 matching lines @@
 
   // Gets a pointer to the opened memory space if it has been
   // Mapped via Map().  Returns NULL if it is not mapped.
   void* memory() const { return memory_; }
 
   // Returns the underlying OS handle for this segment.
   // Use of this handle for anything other than an opaque
   // identifier is not portable.
   SharedMemoryHandle handle() const;
 
+  // Returns the underlying OS handle for this segment. The caller also gets
+  // ownership of the handle. This is logically equivalent to:
+  //   SharedMemoryHandle dup = DuplicateHandle(handle());
+  //   Close();
+  //   return dup;
+  SharedMemoryHandle TakeHandle();

[Nico, 2016/11/14 18:53:51]

make this WARN_UNUSED_RESULT

+
   // Closes the open shared memory segment. The memory will remain mapped if
   // it was previously mapped.
   // It is safe to call Close repeatedly.
   void Close();
 
   // Shares the shared memory to another process.  Attempts to create a
   // platform-specific new_handle which can be used in a remote process to read
   // the shared memory file.  new_handle is an output parameter to receive the
   // handle for use in the remote process.
   //
@@ skipping 71 matching lines @@
   size_t             mapped_size_;
   void*              memory_;
   bool               read_only_;
   size_t             requested_size_;
 
   DISALLOW_COPY_AND_ASSIGN(SharedMemory);
 };
 }  // namespace base
 
 #endif  // BASE_MEMORY_SHARED_MEMORY_H_