gpu: Generate mailboxes on client side

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 <string.h>
 
 #include "gpu/command_buffer/common/types.h"
 #include "gpu/gpu_export.h"
 
 // From gl2/gl2ext.h.
 #ifndef GL_MAILBOX_SIZE_CHROMIUM
 #define GL_MAILBOX_SIZE_CHROMIUM 64
 #endif
 
 namespace gpu {
 
 struct GPU_EXPORT Mailbox {
   Mailbox();
   bool IsZero() const;
   void SetZero();
   void SetName(const int8* name);
+
+  // Generate a unique unguessable mailbox name.
+  static Mailbox Generate();
+
+  // Verify that the mailbox was created through Mailbox::Generate. This only
+  // works in Debug (always returns true in Release). This is not a secure
+  // check, only to catch bugs where clients forgot to call Mailbox::Generate.
+  bool Verify() const;
+
   int8 name[GL_MAILBOX_SIZE_CHROMIUM];
   bool operator<(const Mailbox& other) const {
     return memcmp(this, &other, sizeof other) < 0;
   }
   bool operator==(const Mailbox& other) const {
     return memcmp(this, &other, sizeof other) == 0;
   }
   bool operator!=(const Mailbox& other) const {
     return !operator==(other);
   }
 };
 
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_MAILBOX_H_