Standardize usage of virtual/override/final in media/

media/cast/test/loopback_transport.h

Index: media/cast/test/loopback_transport.h
diff --git a/media/cast/test/loopback_transport.h b/media/cast/test/loopback_transport.h
index 64d99e6c3a682d383ede88148806bea89b0a8f4e..2aca2f3469e075e0a770b1b2e1225fe817890655 100644
--- a/media/cast/test/loopback_transport.h
+++ b/media/cast/test/loopback_transport.h
@@ -27,12 +27,11 @@ class LoopBackTransport : public PacketSender {
  public:
   explicit LoopBackTransport(
       scoped_refptr<CastEnvironment> cast_environment);
-  virtual ~LoopBackTransport();
+  ~LoopBackTransport() override;
 
-  virtual bool SendPacket(PacketRef packet,
-                          const base::Closure& cb) override;
+  bool SendPacket(PacketRef packet, const base::Closure& cb) override;
 
-  virtual int64 GetBytesSent() override;
+  int64 GetBytesSent() override;
 
   // Initiailize this loopback transport.
   // Establish a flow of packets from |pipe| to |packet_receiver|.