Standardize usage of virtual/override/final in mojo/

mojo/edk/system/waiter_unittest.cc

 // Copyright 2013 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.
 
 // NOTE(vtl): Some of these tests are inherently flaky (e.g., if run on a
 // heavily-loaded system). Sorry. |test::EpsilonTimeout()| may be increased to
 // increase tolerance and reduce observed flakiness (though doing so reduces the
 // meaningfulness of the test).
 
 #include "mojo/edk/system/waiter.h"
@@ skipping 19 matching lines @@
  public:
   explicit WaitingThread(MojoDeadline deadline)
       : base::SimpleThread("waiting_thread"),
         deadline_(deadline),
         done_(false),
         result_(MOJO_RESULT_UNKNOWN),
         context_(static_cast<uint32_t>(-1)) {
     waiter_.Init();
   }
 
-  virtual ~WaitingThread() { Join(); }
+  ~WaitingThread() override { Join(); }
 
   void WaitUntilDone(MojoResult* result,
                      uint32_t* context,
                      base::TimeDelta* elapsed) {
     for (;;) {
       {
         base::AutoLock locker(lock_);
         if (done_) {
           *result = result_;
           *context = context_;
           *elapsed = elapsed_;
           break;
         }
       }
 
       base::PlatformThread::Sleep(
           base::TimeDelta::FromMicroseconds(kPollTimeMicros));
     }
   }
 
   Waiter* waiter() { return &waiter_; }
 
  private:
-  virtual void Run() override {
+  void Run() override {
     test::Stopwatch stopwatch;
     MojoResult result;
     uint32_t context = static_cast<uint32_t>(-1);
     base::TimeDelta elapsed;
 
     stopwatch.Start();
     result = waiter_.Wait(deadline_, &context);
     elapsed = stopwatch.Elapsed();
 
     {
@@ skipping 218 matching lines @@
     EXPECT_EQ(MOJO_RESULT_FAILED_PRECONDITION, result);
     EXPECT_EQ(7u, context);
     EXPECT_GT(elapsed, (1 - 1) * test::EpsilonTimeout());
     EXPECT_LT(elapsed, (1 + 1) * test::EpsilonTimeout());
   }
 }
 
 }  // namespace
 }  // namespace system
 }  // namespace mojo