Standardize usage of virtual/override/final in mojo/

mojo/public/cpp/environment/lib/default_async_waiter.cc

 // 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.
 
 #include "mojo/public/cpp/environment/lib/default_async_waiter.h"
 
 #include <assert.h>
 
 #include "mojo/public/c/environment/async_waiter.h"
 #include "mojo/public/cpp/utility/run_loop.h"
 #include "mojo/public/cpp/utility/run_loop_handler.h"
 
 namespace mojo {
 
 namespace {
 
 // RunLoopHandler implementation used for a request to AsyncWait(). There are
 // two ways RunLoopHandlerImpl is deleted:
 // . when the handle is ready (or errored).
 // . when CancelWait() is invoked.
 class RunLoopHandlerImpl : public RunLoopHandler {
  public:
   RunLoopHandlerImpl(const Handle& handle,
                      MojoAsyncWaitCallback callback,
                      void* closure)
       : handle_(handle), callback_(callback), closure_(closure) {}
 
-  virtual ~RunLoopHandlerImpl() { RunLoop::current()->RemoveHandler(handle_); }
+  ~RunLoopHandlerImpl() override { RunLoop::current()->RemoveHandler(handle_); }
 
   // RunLoopHandler:
-  virtual void OnHandleReady(const Handle& handle) override {
+  void OnHandleReady(const Handle& handle) override {
     NotifyCallback(MOJO_RESULT_OK);
   }
 
-  virtual void OnHandleError(const Handle& handle, MojoResult result) override {
+  void OnHandleError(const Handle& handle, MojoResult result) override {
     NotifyCallback(result);
   }
 
  private:
   void NotifyCallback(MojoResult result) {
     // Delete this to unregister the handle. That way if the callback
     // reregisters everything is ok.
     MojoAsyncWaitCallback callback = callback_;
     void* closure = closure_;
     delete this;
@@ skipping 30 matching lines @@
 
 }  // namespace
 
 namespace internal {
 
 const MojoAsyncWaiter kDefaultAsyncWaiter = {AsyncWait, CancelWait};
 
 }  // namespace internal
 
 }  // namespace mojo