Standardize usage of virtual/override/final in sandbox/

sandbox/mac/xpc_message_server_unittest.cc

Index: sandbox/mac/xpc_message_server_unittest.cc
diff --git a/sandbox/mac/xpc_message_server_unittest.cc b/sandbox/mac/xpc_message_server_unittest.cc
index af8280e4a21b493a798a390bdca358bcae693e09..734096cda1fa337e34784d0baaa7f5ba20718b0d 100644
--- a/sandbox/mac/xpc_message_server_unittest.cc
+++ b/sandbox/mac/xpc_message_server_unittest.cc
@@ -43,7 +43,7 @@ class BlockDemuxer : public MessageDemuxer {
         pipe_(NULL) {
   }
 
-  virtual ~BlockDemuxer() {
+  ~BlockDemuxer() override {
     if (pipe_)
       xpc_release(pipe_);
     if (demux_block_)
@@ -68,7 +68,7 @@ class BlockDemuxer : public MessageDemuxer {
     return true;
   }
 
-  virtual void DemuxMessage(IPCMessage request) override {
+  void DemuxMessage(IPCMessage request) override {
     demux_block_(request);
   }