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/asyncudpsocket.h b/webrtc/base/asyncudpsocket.h
index ac64dca..4b47007 100644
--- a/webrtc/base/asyncudpsocket.h
+++ b/webrtc/base/asyncudpsocket.h
@@ -31,21 +31,24 @@
   static AsyncUDPSocket* Create(SocketFactory* factory,
                                 const SocketAddress& bind_address);
   explicit AsyncUDPSocket(AsyncSocket* socket);
-  virtual ~AsyncUDPSocket();
+  ~AsyncUDPSocket() override;
 
-  virtual SocketAddress GetLocalAddress() const;
-  virtual SocketAddress GetRemoteAddress() const;
-  virtual int Send(const void *pv, size_t cb,
-                   const rtc::PacketOptions& options);
-  virtual int SendTo(const void *pv, size_t cb, const SocketAddress& addr,
-                     const rtc::PacketOptions& options);
-  virtual int Close();
+  SocketAddress GetLocalAddress() const override;
+  SocketAddress GetRemoteAddress() const override;
+  int Send(const void* pv,
+           size_t cb,
+           const rtc::PacketOptions& options) override;
+  int SendTo(const void* pv,
+             size_t cb,
+             const SocketAddress& addr,
+             const rtc::PacketOptions& options) override;
+  int Close() override;
 
-  virtual State GetState() const;
-  virtual int GetOption(Socket::Option opt, int* value);
-  virtual int SetOption(Socket::Option opt, int value);
-  virtual int GetError() const;
-  virtual void SetError(int error);
+  State GetState() const override;
+  int GetOption(Socket::Option opt, int* value) override;
+  int SetOption(Socket::Option opt, int value) override;
+  int GetError() const override;
+  void SetError(int error) override;
 
  private:
   // Called when the underlying socket is ready to be read from.