Revert "Enable the clang style plugin in rtc_base/"

This reverts commit af551a1956d2ec3a388cf7e0e88c7ee2c2b61291.

Reason for revert: Fails to compile on Chromium FYI bot: https://build.chromium.org/p/chromium.webrtc.fyi/builders/Linux%20Builder/builds/21375

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}

TBR=steveanton@webrtc.org,kwiberg@webrtc.org

Change-Id: Iafdf4bc1744a981b5d7d38e4a0c5b2d88753f00a
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:163
Reviewed-on: https://webrtc-review.googlesource.com/14740
Reviewed-by: Steve Anton <steveanton@webrtc.org>
Commit-Queue: Steve Anton <steveanton@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20402}
diff --git a/rtc_base/nullsocketserver_unittest.cc b/rtc_base/nullsocketserver_unittest.cc
index e3d9952..29f4980 100644
--- a/rtc_base/nullsocketserver_unittest.cc
+++ b/rtc_base/nullsocketserver_unittest.cc
@@ -18,9 +18,12 @@
 class NullSocketServerTest
     : public testing::Test,
       public MessageHandler {
+ public:
+  NullSocketServerTest() {}
  protected:
-  void OnMessage(Message* message) override { ss_.WakeUp(); }
-
+  virtual void OnMessage(Message* message) {
+    ss_.WakeUp();
+  }
   NullSocketServer ss_;
 };