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/physicalsocketserver_unittest.cc b/rtc_base/physicalsocketserver_unittest.cc
index 36d1881..2320e97 100644
--- a/rtc_base/physicalsocketserver_unittest.cc
+++ b/rtc_base/physicalsocketserver_unittest.cc
@@ -506,11 +506,9 @@
   }
 
  protected:
-  void SetUp() {
-    ss_.reset(new PhysicalSocketServer());
-  }
+  void SetUp() override { ss_.reset(new PhysicalSocketServer()); }
 
-  void TearDown() {
+  void TearDown() override {
     ss_.reset(nullptr);
     signals_received_.clear();
     signaled_thread_ = nullptr;
@@ -584,7 +582,7 @@
 }
 
 class RaiseSigTermRunnable : public Runnable {
-  void Run(Thread *thread) {
+  void Run(Thread* thread) override {
     thread->socketserver()->Wait(1000, false);
 
     // Allow SIGTERM. This will be the only thread with it not masked so it will