Reland "Enable the clang style plugin in rtc_base/"

This is a reland of Id63f0deb7b335690157ab157c35177b7836688da.

Original change's description:
> Enable the clang style plugin in rtc_base/
> 
> Enabled the plugin and cleaned up all issues it found.
> 
> Bug: webrtc:163
> Change-Id: Id63f0deb7b335690157ab157c35177b7836688da
> Reviewed-on: https://webrtc-review.googlesource.com/14660
> Commit-Queue: Steve Anton <steveanton@webrtc.org>
> Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#20401}

Bug: webrtc:163
Change-Id: I861a5fe741215115b0e7a2be9c0786836ff5376e
Reviewed-on: https://webrtc-review.googlesource.com/15040
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Steve Anton <steveanton@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20416}
diff --git a/rtc_base/virtualsocket_unittest.cc b/rtc_base/virtualsocket_unittest.cc
index 785d32c..6081346 100644
--- a/rtc_base/virtualsocket_unittest.cc
+++ b/rtc_base/virtualsocket_unittest.cc
@@ -53,7 +53,7 @@
     return 1000 * size / rate;
   }
 
-  void OnMessage(Message* pmsg) {
+  void OnMessage(Message* pmsg) override {
     ASSERT_EQ(1u, pmsg->message_id);
 
     if (done)
@@ -98,9 +98,7 @@
     thread->PostDelayed(RTC_FROM_HERE, 1000, this, 1);
   }
 
-  ~Receiver() {
-    thread->Clear(this);
-  }
+  ~Receiver() override { thread->Clear(this); }
 
   void OnReadPacket(AsyncPacketSocket* s, const char* data, size_t size,
                     const SocketAddress& remote_addr,
@@ -119,7 +117,7 @@
     samples += 1;
   }
 
-  void OnMessage(Message* pmsg) {
+  void OnMessage(Message* pmsg) override {
     ASSERT_EQ(1u, pmsg->message_id);
 
     if (done)