Fix clang style warnings in webrtc/base

Mostly this consists of marking functions with override when
applicable, and moving function bodies from .h to .cc files.

Not inlining virtual functions with simple bodies such as

  { return false; }

strikes me as probably losing more in readability than we gain in
binary size and compilation time, but I guess it's just like any other
case where enabling a generally good warning forces us to write
slightly worse code in a couple of places.

BUG=163
R=kjellander@webrtc.org, tommi@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/47429004

Cr-Commit-Position: refs/heads/master@{#8656}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8656 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/base/messagequeue.h

@@ -192,14 +192,14 @@ class MessageQueue {
   virtual bool Peek(Message *pmsg, int cmsWait = 0);
   virtual void Post(MessageHandler *phandler, uint32 id = 0,
                     MessageData *pdata = NULL, bool time_sensitive = false);
-  virtual void PostDelayed(int cmsDelay, MessageHandler *phandler,
-                           uint32 id = 0, MessageData *pdata = NULL) {
-    return DoDelayPost(cmsDelay, TimeAfter(cmsDelay), phandler, id, pdata);
-  }
-  virtual void PostAt(uint32 tstamp, MessageHandler *phandler,
-                      uint32 id = 0, MessageData *pdata = NULL) {
-    return DoDelayPost(TimeUntil(tstamp), tstamp, phandler, id, pdata);
-  }
+  virtual void PostDelayed(int cmsDelay,
+                           MessageHandler* phandler,
+                           uint32 id = 0,
+                           MessageData* pdata = NULL);
+  virtual void PostAt(uint32 tstamp,
+                      MessageHandler* phandler,
+                      uint32 id = 0,
+                      MessageData* pdata = NULL);
   virtual void Clear(MessageHandler *phandler, uint32 id = MQID_ANY,
                      MessageList* removed = NULL);
   virtual void Dispatch(Message *pmsg);