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

webrtc/base/timeutils.h

Index: webrtc/base/timeutils.h
diff --git a/webrtc/base/timeutils.h b/webrtc/base/timeutils.h
index 78ebacee38df5087737de039fa20a6e8c485c9f6..06cc36b5ee0e41443ddca8c45b5f3f0ec02ca9fd 100644
--- a/webrtc/base/timeutils.h
+++ b/webrtc/base/timeutils.h
@@ -39,6 +39,8 @@ class ClockInterface {
 
 // Sets the global source of time. This is useful mainly for unit tests.
 //
+// Returns the previously set ClockInterface, or nullptr if none is set.
+//
 // Does not transfer ownership of the clock.
 // SetClock(nullptr) should be called before the ClockInterface is deleted.
 //
@@ -49,7 +51,7 @@ class ClockInterface {
 // TODO(deadbeef): Instead of having functions that access this global
 // ClockInterface, we may want to pass the ClockInterface into everything
 // that uses it, eliminating the need for a global variable and this function.
-void SetClock(ClockInterface* clock);
+ClockInterface* SetClock(ClockInterface* clock);

[tommi, 2016/06/02 07:59:01]

Can we rename this method to SetClockForTesting?  I think it could have bad
consequences if we allow changing this value outside of tests.  Even with tests,
it could be bad if we have tests executing in parallel.

[Taylor Brandstetter, 2016/06/02 17:19:54]

Done.

 
 // Returns the current time in milliseconds in 32 bits.
 uint32_t Time32();