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

webrtc/base/fakeclock.cc

 /*
  *  Copyright 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #include "webrtc/base/fakeclock.h"
 
 #include "webrtc/base/checks.h"
 #include "webrtc/base/messagequeue.h"
 
 namespace rtc {
 
 uint64_t FakeClock::TimeNanos() const {
   CritScope cs(&lock_);
   return time_;
 }
 
 void FakeClock::SetTimeNanos(uint64_t nanos) {
   {
     CritScope cs(&lock_);
     RTC_DCHECK(nanos >= time_);
     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