Revert of Improving the fake clock and using it to fix a flaky STUN timeout test.

webrtc/base/signalthread_unittest.cc

Index: webrtc/base/signalthread_unittest.cc
diff --git a/webrtc/base/signalthread_unittest.cc b/webrtc/base/signalthread_unittest.cc
index 0029acf5d966b7ee6bab05f4ba4e474dab179387..bbae91daf0faf94ebb9837461d8af8acb14b1252 100644
--- a/webrtc/base/signalthread_unittest.cc
+++ b/webrtc/base/signalthread_unittest.cc
@@ -140,9 +140,6 @@
 // signal thread is still working.  This may happen
 // when shutting down the process.
 TEST_F(SignalThreadTest, OwnerThreadGoesAway) {
-  // We don't use |thread_| for this test, so destroy it.
-  thread_->Destroy(true);
-
   {
     std::unique_ptr<OwnerThread> owner(new OwnerThread(this));
     main_thread_ = owner.get();