Fixing and enhancing OrderedSimpleTaskRunner to allow 100% deterministic tests.

cc/test/scheduler_test_common.cc

Index: cc/test/scheduler_test_common.cc
diff --git a/cc/test/scheduler_test_common.cc b/cc/test/scheduler_test_common.cc
index 3b35a54a9b713423dd91c55b428dc6997937f01c..b928a38cd04c89f3714678ac207dd8a1fbab5060 100644
--- a/cc/test/scheduler_test_common.cc
+++ b/cc/test/scheduler_test_common.cc
@@ -14,4 +14,8 @@ void FakeTimeSourceClient::OnTimerTick() {
 
 base::TimeTicks FakeDelayBasedTimeSource::Now() const { return now_; }
 
+base::TimeTicks TestScheduler::Now() const {
+  return test_task_runner_->Now();
+}
+
 }  // namespace cc