Standardize usage of virtual/override/final specifiers.

media/base/wall_clock_time_source_unittest.cc

Index: media/base/wall_clock_time_source_unittest.cc
diff --git a/media/base/wall_clock_time_source_unittest.cc b/media/base/wall_clock_time_source_unittest.cc
index 2b031516b4cc9aa7891211f3c5d1b218add794f0..08a424d42a406de06e6900d77f2ca8ed15f1c863 100644
--- a/media/base/wall_clock_time_source_unittest.cc
+++ b/media/base/wall_clock_time_source_unittest.cc
@@ -14,7 +14,7 @@ class WallClockTimeSourceTest : public testing::Test {
     time_source_.SetTickClockForTesting(
         scoped_ptr<base::TickClock>(tick_clock_));
   }
-  virtual ~WallClockTimeSourceTest() {}
+  ~WallClockTimeSourceTest() override {}
 
   void AdvanceTimeInSeconds(int seconds) {
     tick_clock_->Advance(base::TimeDelta::FromSeconds(seconds));