Cast: Add tests for clocks being slow/fast

media/cast/test/skewed_tick_clock.cc

+// 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.
+
+#include "media/cast/test/skewed_tick_clock.h"
+
+#include "base/time/time.h"
+
+namespace media {
+namespace cast {
+namespace test {
+
+SkewedTickClock::SkewedTickClock(base::TickClock* clock)
+    : clock_(clock),
+      skew_(1.0),
+      last_skew_set_time_(clock_->NowTicks()),
+      skew_clock_at_last_set_(last_skew_set_time_) {
+}
+
+base::TimeTicks SkewedTickClock::SkewTicks(base::TimeTicks now) {
+  return base::TimeDelta::FromMicroseconds(
+      (now - last_skew_set_time_).InMicroseconds() * skew_) +
+      skew_clock_at_last_set_;
+}
+
+void SkewedTickClock::SetSkew(double skew, base::TimeDelta offset) {
+  base::TimeTicks now = clock_->NowTicks();
+  last_skew_set_time_ = now;
+  skew_clock_at_last_set_ = SkewTicks(now) + offset;
+}
+
+base::TimeTicks SkewedTickClock::NowTicks() {
+  return SkewTicks(clock_->NowTicks());
+}
+
+}  // namespace test
+}  // namespace cast
+}  // namespace media