Fix some chromium-style warnings in webrtc/system_wrappers/

BUG=163
R=henrike@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/1906004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@4464 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/system_wrappers/interface/clock.h b/webrtc/system_wrappers/interface/clock.h
index 177e18f..ce32691 100644
--- a/webrtc/system_wrappers/interface/clock.h
+++ b/webrtc/system_wrappers/interface/clock.h
@@ -55,17 +55,17 @@
 
   // Return a timestamp in milliseconds relative to some arbitrary source; the
   // source is fixed for this clock.
-  virtual int64_t TimeInMilliseconds();
+  virtual int64_t TimeInMilliseconds() OVERRIDE;
 
   // Return a timestamp in microseconds relative to some arbitrary source; the
   // source is fixed for this clock.
-  virtual int64_t TimeInMicroseconds();
+  virtual int64_t TimeInMicroseconds() OVERRIDE;
 
   // Retrieve an NTP absolute timestamp in milliseconds.
-  virtual void CurrentNtp(uint32_t& seconds, uint32_t& fractions);
+  virtual void CurrentNtp(uint32_t& seconds, uint32_t& fractions) OVERRIDE;
 
   // Converts an NTP timestamp to a millisecond timestamp.
-  virtual int64_t CurrentNtpInMilliseconds();
+  virtual int64_t CurrentNtpInMilliseconds() OVERRIDE;
 
   // Advance the simulated clock with a given number of milliseconds or
   // microseconds.