Make chrome/browser/extensions use base::Clock instead of MockTimeProvider

base/test/simple_test_clock.h

 // 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_CLOCK_H_
 #define BASE_SIMPLE_TEST_CLOCK_H_
 
 #include "base/compiler_specific.h"
 #include "base/synchronization/lock.h"
 #include "base/time.h"
 #include "base/time/clock.h"
 
 namespace base {
 
 // SimpleTestClock is a Clock implementation that gives control over
-// the returned Time objects.  All methods can be called from any
+// the returned Time objects.  All methods may be called from any
 // thread.
 class SimpleTestClock : public Clock {
  public:
   // Starts off with a clock set to Time().
   SimpleTestClock();
   virtual ~SimpleTestClock();
 
   virtual Time Now() OVERRIDE;
 
-  // Sets the current time forward by |delta|.  Safe to call from any
-  // thread.
+  // Advances the clock by |delta|.
   void Advance(TimeDelta delta);
 
+  // Sets the clock to the given time.
+  void SetNow(Time now);
+
  private:
   // Protects |now_|.
   Lock lock_;
 
   Time now_;
 };
 
 }  // namespace base
 
 #endif  // BASE_SIMPLE_TEST_CLOCK_H_