Revert of Standardize usage of virtual/override/final in ipc/

ipc/ipc_sync_channel.h

Index: ipc/ipc_sync_channel.h
diff --git a/ipc/ipc_sync_channel.h b/ipc/ipc_sync_channel.h
index 35934850ed7cbf77b2123612648bf86c65d17544..3f62d2f35600af0747258c1055f49497d7b16f57 100644
--- a/ipc/ipc_sync_channel.h
+++ b/ipc/ipc_sync_channel.h
@@ -91,9 +91,9 @@
       const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner,
       base::WaitableEvent* shutdown_event);
 
-  ~SyncChannel() override;
-
-  bool Send(Message* message) override;
+  virtual ~SyncChannel();
+
+  virtual bool Send(Message* message) override;
 
   // Sets the dispatch group for this channel, to only allow re-entrant dispatch
   // of messages to other channels in the same group.
@@ -170,17 +170,17 @@
     base::WaitableEventWatcher::EventCallback MakeWaitableEventCallback();
 
    private:
-    ~SyncContext() override;
+    virtual ~SyncContext();
     // ChannelProxy methods that we override.
 
     // Called on the listener thread.
-    void Clear() override;
+    virtual void Clear() override;
 
     // Called on the IPC thread.
-    bool OnMessageReceived(const Message& msg) override;
-    void OnChannelError() override;
-    void OnChannelOpened() override;
-    void OnChannelClosed() override;
+    virtual bool OnMessageReceived(const Message& msg) override;
+    virtual void OnChannelError() override;
+    virtual void OnChannelOpened() override;
+    virtual void OnChannelClosed() override;
 
     // Cancels all pending Send calls.
     void CancelPendingSends();