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 bbae91daf0faf94ebb9837461d8af8acb14b1252..0029acf5d966b7ee6bab05f4ba4e474dab179387 100644
--- a/webrtc/base/signalthread_unittest.cc
+++ b/webrtc/base/signalthread_unittest.cc
@@ -140,6 +140,9 @@ class OwnerThread : public Thread, public sigslot::has_slots<> {
 // 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();