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

webrtc/base/fakeclock.h

Index: webrtc/base/fakeclock.h
diff --git a/webrtc/base/fakeclock.h b/webrtc/base/fakeclock.h
index 2b3afdde05f684926621bcc95c2f917bfb7bd60f..da41d8dec4a7e65755004fda0f195d712ccafcfc 100644
--- a/webrtc/base/fakeclock.h
+++ b/webrtc/base/fakeclock.h
@@ -19,6 +19,8 @@ namespace rtc {
 
 // Fake clock for use with unit tests, which does not tick on its own.
 // Starts at time 0.
+//
+// TODO(deadbeef): Unify with webrtc::SimulatedClock.
 class FakeClock : public ClockInterface {
  public:
   ~FakeClock() override {}
@@ -38,6 +40,20 @@ class FakeClock : public ClockInterface {
   uint64_t time_ GUARDED_BY(lock_) = 0u;
 };
 
+// Helper class which creates and sets a fake clock as the global clock in
+// its constructor, and unsets and deletes it in its destructor.
+class ScopedFakeClock {

[pthatcher1, 2016/06/01 22:38:14]

Does this work in C++?

class ScopedFakeClock : FakeClock {
 public:
  ScopedFakeClock() { SetClock(this); }
  ~ScopedFakeClock() { SetClock(nullptr); }
}

?

That way, the caller would't have to call "sfc.clock()".  They could just use
the clock.

[Taylor Brandstetter, 2016/06/01 23:28:37]

Done.

+ public:
+  ScopedFakeClock() { SetClock(&clock_); }
+
+  ~ScopedFakeClock() { SetClock(nullptr); }

[pthatcher1, 2016/06/01 22:38:14]

Should we do this?

public:
 ScopedFakeClock() { old_clock_ = g_clock; SetClock(this); }
 ~ScopedFakeClock() { SetClock(old_clock_); }

private:
 old_clock_ = nullptr;



Otherwise, we might blow away a clock that was supposed to be there.  But I
don't know who will set g_clock to anything but nullptr except a unit test.

[Taylor Brandstetter, 2016/06/01 23:28:37]

I hadn't *intended* for there to be multiple fake clocks in use in the same
test. But I guess it's possible, so might as well do this.

+
+  FakeClock& clock() { return clock_; }
+
+ private:
+  FakeClock clock_;
+};
+
 }  // namespace rtc
 
 #endif  // WEBRTC_BASE_FAKECLOCK_H_