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/sslidentity_unittest.cc b/rtc_base/sslidentity_unittest.cc
index 7d9f82c..6932298 100644
--- a/rtc_base/sslidentity_unittest.cc
+++ b/rtc_base/sslidentity_unittest.cc
@@ -207,12 +207,7 @@
 
 class SSLIdentityTest : public testing::Test {
  public:
-  SSLIdentityTest() {}
-
-  ~SSLIdentityTest() {
-  }
-
-  virtual void SetUp() {
+  void SetUp() override {
     identity_rsa1_.reset(SSLIdentity::Generate("test1", rtc::KT_RSA));
     identity_rsa2_.reset(SSLIdentity::Generate("test2", rtc::KT_RSA));
     identity_ecdsa1_.reset(SSLIdentity::Generate("test3", rtc::KT_ECDSA));
@@ -499,7 +494,7 @@
     // Set use of the test RNG to get deterministic expiration timestamp.
     rtc::SetRandomTestMode(true);
   }
-  ~SSLIdentityExpirationTest() {
+  ~SSLIdentityExpirationTest() override {
     // Put it back for the next test.
     rtc::SetRandomTestMode(false);
   }