Convert some more |base::Lock|s to |mojo::system::Mutex|s.

mojo/edk/system/endpoint_relayer.h

 // Copyright 2014 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_EDK_SYSTEM_ENDPOINT_RELAYER_H_
 #define MOJO_EDK_SYSTEM_ENDPOINT_RELAYER_H_
 
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
-#include "base/synchronization/lock.h"
 #include "mojo/edk/system/channel_endpoint_client.h"
+#include "mojo/edk/system/mutex.h"
 #include "mojo/edk/system/system_impl_export.h"
 #include "mojo/public/cpp/system/macros.h"
 
 namespace mojo {
 namespace system {
 
 class ChannelEndpoint;
 
 // This is a simple |ChannelEndpointClient| that just relays messages between
 // two |ChannelEndpoint|s (without the overhead of |MessagePipe|).
@@ skipping 52 matching lines @@
   // |Type::ENDPOINT_CLIENT| messages (see |Filter| above).
   void SetFilter(scoped_ptr<Filter> filter);
 
   // |ChannelEndpointClient| methods:
   bool OnReadMessage(unsigned port, MessageInTransit* message) override;
   void OnDetachFromChannel(unsigned port) override;
 
  private:
   ~EndpointRelayer() override;
 
-  // TODO(vtl): We could probably get away without the lock if we had a
-  // thread-safe |scoped_refptr|.
-  base::Lock lock_;  // Protects the following members.
-  scoped_refptr<ChannelEndpoint> endpoints_[2];
-  scoped_ptr<Filter> filter_;
+  Mutex mutex_;
+  scoped_refptr<ChannelEndpoint> endpoints_[2] MOJO_GUARDED_BY(mutex_);
+  scoped_ptr<Filter> filter_ MOJO_GUARDED_BY(mutex_);
 
   MOJO_DISALLOW_COPY_AND_ASSIGN(EndpointRelayer);
 };
 
 }  // namespace system
 }  // namespace mojo
 
 #endif  // MOJO_EDK_SYSTEM_ENDPOINT_RELAYER_H_