[Cherrypick try #2] Fix computation of runtime for throttled tasks

components/scheduler/renderer/throttled_time_domain.cc

+// Copyright 2016 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 "components/scheduler/renderer/throttled_time_domain.h"
+
+#include "base/time/tick_clock.h"
+
+namespace scheduler {
+
+ThrottledTimeDomain::ThrottledTimeDomain(TimeDomain::Observer* observer,
+                                         base::TickClock* tick_clock)
+    : VirtualTimeDomain(observer, tick_clock->NowTicks()),
+      tick_clock_(tick_clock) {}
+
+ThrottledTimeDomain::~ThrottledTimeDomain() {}
+
+base::TimeTicks ThrottledTimeDomain::ComputeDelayedRunTime(
+    base::TimeTicks,
+    base::TimeDelta delay) const {
+  // We ignore the |time_domain_now| parameter since its the virtual time but we
+  // need to use the current real time when computing the delayed runtime.  If
+  // don't do that, throttled timers may fire sooner than expected.
+  return tick_clock_->NowTicks() + delay;
+}
+
+const char* ThrottledTimeDomain::GetName() const {
+  return "ThrottledTimeDomain";
+}
+
+}  // namespace scheduler