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
diff --git a/webrtc/base/messagequeue.cc b/webrtc/base/messagequeue.cc
index 3706898..53e451f 100644
--- a/webrtc/base/messagequeue.cc
+++ b/webrtc/base/messagequeue.cc
@@ -297,6 +297,20 @@
   ss_->WakeUp();
 }
 
+void MessageQueue::PostDelayed(int cmsDelay,
+                               MessageHandler* phandler,
+                               uint32 id,
+                               MessageData* pdata) {
+  return DoDelayPost(cmsDelay, TimeAfter(cmsDelay), phandler, id, pdata);
+}
+
+void MessageQueue::PostAt(uint32 tstamp,
+                          MessageHandler* phandler,
+                          uint32 id,
+                          MessageData* pdata) {
+  return DoDelayPost(TimeUntil(tstamp), tstamp, phandler, id, pdata);
+}
+
 void MessageQueue::DoDelayPost(int cmsDelay, uint32 tstamp,
     MessageHandler *phandler, uint32 id, MessageData* pdata) {
   if (fStop_)