Make mojo_system static and mojo_system_impl a component, never use both

mojo/embedder/embedder.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_EMBEDDER_EMBEDDER_H_
 #define MOJO_EMBEDDER_EMBEDDER_H_
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "base/task_runner.h"
 #include "mojo/embedder/scoped_platform_handle.h"
 #include "mojo/public/cpp/system/core.h"
 #include "mojo/system/system_impl_export.h"
 
 namespace mojo {
 namespace embedder {
 
-// Must be called first to initialize the (global, singleton) system.
-MOJO_SYSTEM_IMPL_EXPORT void Init();
-
 // Creates a new "channel", returning a handle to the bootstrap message pipe on
 // that channel. |platform_handle| should be an OS-dependent handle to one side
 // of a suitable bidirectional OS "pipe" (e.g., a file descriptor to a socket on
 // POSIX, a handle to a named pipe on Windows); this "pipe" should be connected
 // and ready for operation (e.g., to be written to or read from).
 // |io_thread_task_runner| should be a |TaskRunner| for the thread on which the
 // "channel" will run (read data and demultiplex).
 //
 // On completion, it will run |callback| with a pointer to a |ChannelInfo|
 // (which is meant to be opaque to the embedder). If
@@ skipping 22 matching lines @@
     DidCreateChannelCallback callback,
     scoped_refptr<base::TaskRunner> callback_thread_task_runner);
 
 MOJO_SYSTEM_IMPL_EXPORT void DestroyChannelOnIOThread(
     ChannelInfo* channel_info);
 
 }  // namespace embedder
 }  // namespace mojo
 
 #endif  // MOJO_EMBEDDER_EMBEDDER_H_