Update VirtualSocketServerTest to use a fake clock.

webrtc/base/timeutils.h

Index: webrtc/base/timeutils.h
diff --git a/webrtc/base/timeutils.h b/webrtc/base/timeutils.h
index be9edabf2da357e00c4a9b2027fedb3dbfafe012..735af4a9f46c6dd1d610f4fe2b564104bb599e6d 100644
--- a/webrtc/base/timeutils.h
+++ b/webrtc/base/timeutils.h
@@ -53,6 +53,9 @@ class ClockInterface {
 // that uses it, eliminating the need for a global variable and this function.
 ClockInterface* SetClockForTesting(ClockInterface* clock);
 
+// Returns previously set clock, or nullptr if no custom clock is being used.
+ClockInterface* GetClockForTesting();
+
 // Returns the actual system time, even if a clock is set for testing.
 // Useful for timeouts while using a test clock, or for logging.
 int64_t SystemTimeNanos();