Reduce GPU mailbox size to 16 bytes

gpu/command_buffer/common/mailbox.h

 // Copyright 2013 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_MAILBOX_H_
 #define GPU_COMMAND_BUFFER_MAILBOX_H_
 
 #include <stdint.h>
 #include <string.h>
 
 #include "gpu/gpu_export.h"
 
 // From gl2/gl2ext.h.
 #ifndef GL_MAILBOX_SIZE_CHROMIUM
-#define GL_MAILBOX_SIZE_CHROMIUM 64
+#define GL_MAILBOX_SIZE_CHROMIUM 16
 #endif
 
 namespace gpu {
 
 // A mailbox is an unguessable name that references texture image data.
 // This name can be passed across processes permitting one context to share
 // texture image data with another. The mailbox name consists of a random
 // set of bytes, optionally with a checksum (in debug mode) to verify the
 // name is valid.
 // See src/gpu/GLES2/extensions/CHROMIUM/CHROMIUM_texture_mailbox.txt for more
@@ skipping 30 matching lines @@
   }
   bool operator!=(const Mailbox& other) const {
     return !operator==(other);
   }
 };
 
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_MAILBOX_H_