Refactor rtc_unittests into several targets.

webrtc/base/logging_unittest.cc

Index: webrtc/base/logging_unittest.cc
diff --git a/webrtc/base/logging_unittest.cc b/webrtc/base/logging_unittest.cc
index c08b1efd4a1cb4a4b1aba96b7beda40f69c42b8e..50350353696593fad8ebce7464e22309c0220211 100644
--- a/webrtc/base/logging_unittest.cc
+++ b/webrtc/base/logging_unittest.cc
@@ -88,12 +88,12 @@ TEST(LogTest, MultipleStreams) {
 // We should restore the correct global state at the end.
 class LogThread : public Thread {
  public:
-  virtual ~LogThread() {
+  ~LogThread() override {
     Stop();
   }
 
  private:
-  void Run() {
+  void Run() override {
     // LS_SENSITIVE to avoid cluttering up any real logging going on
     LOG(LS_SENSITIVE) << "LOG";
   }