[mojo] Use base::Pickle for Message storage.

mojo/public/cpp/bindings/lib/message_builder.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 MOJO_PUBLIC_CPP_BINDINGS_LIB_MESSAGE_BUILDER_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_LIB_MESSAGE_BUILDER_H_
 
 #include <stdint.h>
 
-#include "mojo/public/cpp/bindings/lib/fixed_buffer.h"
 #include "mojo/public/cpp/bindings/lib/message_internal.h"
 #include "mojo/public/cpp/bindings/message.h"
 
 namespace mojo {
 class Message;
 
 namespace internal {
 
 class MessageBuilder {
  public:
   MessageBuilder(uint32_t name, size_t payload_size);
   ~MessageBuilder();
 
-  Buffer* buffer() { return &buf_; }
+  Buffer* buffer() { return message_.buffer(); }
   Message* message() { return &message_; }
 
  protected:
   MessageBuilder();
-  void Initialize(size_t size);
+  void InitializeMessage(size_t size);
 
   Message message_;
-  FixedBuffer buf_;
 
   MOJO_DISALLOW_COPY_AND_ASSIGN(MessageBuilder);
 };
 
 class MessageWithRequestIDBuilder : public MessageBuilder {
  public:
   MessageWithRequestIDBuilder(uint32_t name,
                               size_t payload_size,
                               uint32_t flags,
                               uint64_t request_id);
@@ skipping 16 matching lines @@
       : MessageWithRequestIDBuilder(name,
                                     payload_size,
                                     kMessageIsResponse,
                                     request_id) {}
 };
 
 }  // namespace internal
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_LIB_MESSAGE_BUILDER_H_