Cast: Add tests for clocks being slow/fast

media/cast/test/skewed_tick_clock.h

+// Copyright 2014 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 CAST_MEDIA_TEST_SKEWED_TICK_CLOCK_H
+#define CAST_MEDIA_TEST_SKEWED_TICK_CLOCK_H
+
+#include "base/time/tick_clock.h"
+#include "base/time/time.h"
+
+namespace media {
+namespace cast {
+namespace test {
+
+// Wraps a base::TickClock, and lets you change the speed and offset
+// of time compared to the wrapped clock. See SetSkew for how usage.
+class SkewedTickClock : public base::TickClock {
+ public:
+  // Does not take ownership of |clock_|.
+  explicit SkewedTickClock(base::TickClock* clock_);
+  // |skew| > 1.0 means clock runs faster.
+  // |offset| > 0 means clock returns times from the future.
+  // Note, |offset| is cumulative.
+  // Also note that changing the skew will never make the clock
+  // jump forwards or backwards, only changing the offset will
+  // do that.
+  void SetSkew(double skew, base::TimeDelta offset);
+  virtual base::TimeTicks NowTicks() OVERRIDE;
+
+ private:
+  base::TimeTicks SkewTicks(base::TimeTicks now);
+  base::TickClock* clock_;  // Not owned.
+  double skew_;
+  base::TimeTicks last_skew_set_time_;
+  base::TimeTicks skew_clock_at_last_set_;
+
+  DISALLOW_COPY_AND_ASSIGN(SkewedTickClock);
+};
+
+}  // namespace test
+}  // namespace cast
+}  // namespace media
+
+#endif  // CAST_MEDIA_TEST_SKEWED_TICK_CLOCK_H