Adding the ability to use a simulated clock for unit tests.

webrtc/base/fakeclock.cc

Index: webrtc/base/fakeclock.cc
diff --git a/webrtc/base/fakeclock.cc b/webrtc/base/fakeclock.cc
new file mode 100644
index 0000000000000000000000000000000000000000..e5aa3bc0a4fc3af0aecd8e58b395c54ce48f0d41
--- /dev/null
+++ b/webrtc/base/fakeclock.cc
@@ -0,0 +1,40 @@
+/*
+ *  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();
+}
+
+void FakeClock::AdvanceTime(TimeDelta delta) {
+  CritScope cs(&lock_);
+  SetTimeNanos(time_ + delta.ToNanoseconds());
+}
+
+}  // namespace rtc