Update {virtual,override} to follow C++11 style in media.

media/audio/cras/cras_input_unittest.cc

Index: media/audio/cras/cras_input_unittest.cc
diff --git a/media/audio/cras/cras_input_unittest.cc b/media/audio/cras/cras_input_unittest.cc
index 4113f582451419d9c29f1bec67c275d87f24b229..c3e3ca81d175f80ad01d5eb3ba9ed2ff8488bc0a 100644
--- a/media/audio/cras/cras_input_unittest.cc
+++ b/media/audio/cras/cras_input_unittest.cc
@@ -41,7 +41,7 @@ class MockAudioManagerCrasInput : public AudioManagerCras {
   // of active output streams. It is because the number of active streams
   // is managed inside MakeAudioInputStream, and we don't use
   // MakeAudioInputStream to create the stream in the tests.
-  virtual void ReleaseInputStream(AudioInputStream* stream) override {
+  void ReleaseInputStream(AudioInputStream* stream) override {
     DCHECK(stream);
     delete stream;
   }