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

webrtc/base/fakeclock.cc

Index: webrtc/base/fakeclock.cc
diff --git a/webrtc/base/fakeclock.cc b/webrtc/base/fakeclock.cc
index e5aa3bc0a4fc3af0aecd8e58b395c54ce48f0d41..bcd720ff742f2687f6c0bb05c5e60672edec6314 100644
--- a/webrtc/base/fakeclock.cc
+++ b/webrtc/base/fakeclock.cc
@@ -27,14 +27,24 @@ void FakeClock::SetTimeNanos(uint64_t nanos) {
     time_ = nanos;
   }
   // If message queues are waiting in a socket select() with a timeout provided
-  // by the OS, they should wake up to check if there are any messages ready to
-  // be dispatched based on the fake time.
-  MessageQueueManager::WakeAllMessageQueues();
+  // by the OS, they should wake up and dispatch all messages that are ready.
+  MessageQueueManager::ProcessAllMessageQueues();
 }
 
 void FakeClock::AdvanceTime(TimeDelta delta) {
-  CritScope cs(&lock_);
-  SetTimeNanos(time_ + delta.ToNanoseconds());
+  {
+    CritScope cs(&lock_);
+    time_ += delta.ToNanoseconds();
+  }
+  MessageQueueManager::ProcessAllMessageQueues();
+}
+
+ScopedFakeClock::ScopedFakeClock() {
+  prev_clock_ = SetClockForTesting(this);
+}
+
+ScopedFakeClock::~ScopedFakeClock() {
+  SetClockForTesting(prev_clock_);

[nisse-webrtc, 2016/06/08 09:47:30]

I think it's simpler to only ever allow one fake clock to be in use. I.e., let
the constructor RTC_CHECK that the old value was null, an let the destructor set
it back to null.

Or else, add an RTC_CHECK to the destructor to verify that the return value of
SetClockForTesting is |this|.

 }
 
 }  // namespace rtc