Add a Clock and TickClock interface for mocking out time

base/test/simple_test_tick_clock.h

Index: base/test/simple_test_tick_clock.h
diff --git a/base/test/simple_test_tick_clock.h b/base/test/simple_test_tick_clock.h
new file mode 100644
index 0000000000000000000000000000000000000000..c53301b397379fa13f1d0d49a8f128e5961c3d1e
--- /dev/null
+++ b/base/test/simple_test_tick_clock.h
@@ -0,0 +1,39 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_SIMPLE_TEST_TICK_CLOCK_H_
+#define BASE_SIMPLE_TEST_TICK_CLOCK_H_
+
+#include "base/compiler_specific.h"
+#include "base/synchronization/lock.h"
+#include "base/time.h"
+#include "base/time/tick_clock.h"
+
+namespace base {
+
+// SimpleTestTickClock is a TickClock implementation that gives
+// control over the returned TimeTicks objects.  All methods can be
+// called from any thread.
+class SimpleTestTickClock : public TickClock {
+ public:
+  // Starts off with a clock set to TimeTicks().
+  SimpleTestTickClock();
+  virtual ~SimpleTestTickClock();
+
+  virtual TimeTicks NowTicks() OVERRIDE;
+
+  // Sets the current time forward by |delta|.  Safe to call from any
+  // thread.
+  void Advance(TimeDelta delta);
+
+ private:
+  // Protects |now_ticks_|.
+  Lock lock_;
+
+  TimeTicks now_ticks_;
+};
+
+}  // namespace base
+
+#endif  // BASE_SIMPLE_TEST_TICK_CLOCK_H_