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

ipc/mojo/ipc_channel_mojo_host.cc

Index: ipc/mojo/ipc_channel_mojo_host.cc
diff --git a/ipc/mojo/ipc_channel_mojo_host.cc b/ipc/mojo/ipc_channel_mojo_host.cc
index beb18ee5e99ffc53d7159d1b6cb4c68b8cdcd398..6f9075ae233c4767c9fec1b5bb53a5732615ec6c 100644
--- a/ipc/mojo/ipc_channel_mojo_host.cc
+++ b/ipc/mojo/ipc_channel_mojo_host.cc
@@ -17,12 +17,12 @@
 class ChannelMojoHost::ChannelDelegate : public ChannelMojo::Delegate {
  public:
   explicit ChannelDelegate(scoped_refptr<base::TaskRunner> io_task_runner);
-  ~ChannelDelegate() override;
+  virtual ~ChannelDelegate();
 
   // ChannelMojo::Delegate
-  base::WeakPtr<Delegate> ToWeakPtr() override;
-  void OnChannelCreated(base::WeakPtr<ChannelMojo> channel) override;
-  scoped_refptr<base::TaskRunner> GetIOTaskRunner() override;
+  virtual base::WeakPtr<Delegate> ToWeakPtr() override;
+  virtual void OnChannelCreated(base::WeakPtr<ChannelMojo> channel) override;
+  virtual scoped_refptr<base::TaskRunner> GetIOTaskRunner() override;
 
   // Returns an weak ptr of ChannelDelegate instead of Delegate
   base::WeakPtr<ChannelDelegate> GetWeakPtr();