Rename "register" -> "subscribe" in the Push Messaging code.

content/child/push_messaging/push_dispatcher.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 CONTENT_CHILD_PUSH_MESSAGING_PUSH_DISPATCHER_H_
 #define CONTENT_CHILD_PUSH_MESSAGING_PUSH_DISPATCHER_H_
 
 #include <map>
 
 #include "base/synchronization/lock.h"
 #include "content/child/worker_thread_message_filter.h"
 
 namespace content {
 
 class PushDispatcher : public WorkerThreadMessageFilter {
  public:
   explicit PushDispatcher(ThreadSafeSender* thread_safe_sender);
 
   // Generates a process-unique new request id. Stores it in a map as key to
   // |thread_id| and returns it. This method can be called on any thread.
-  // Note that the registration requests from document contexts do not go via
+  // Note that the subscription requests from document contexts do not go via
   // this class and their request ids may overlap with the ones generated here.
   int GenerateRequestId(int thread_id);
 
  protected:
   ~PushDispatcher() override;
 
  private:
   // WorkerThreadMessageFilter:
   bool ShouldHandleMessage(const IPC::Message& msg) const override;
   void OnFilteredMessageReceived(const IPC::Message& msg) override;
   bool GetWorkerThreadIdForMessage(const IPC::Message& msg,
                                    int* ipc_thread_id) override;
 
   base::Lock request_id_map_lock_;
   std::map<int, int> request_id_map_;  // Maps request id to thread id.
   int next_request_id_;
 
   DISALLOW_COPY_AND_ASSIGN(PushDispatcher);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_CHILD_PUSH_MESSAGING_PUSH_DISPATCHER_H_