Fixing and enhancing OrderedSimpleTaskRunner to allow 100% deterministic tests.

cc/scheduler/scheduler.h

Index: cc/scheduler/scheduler.h
diff --git a/cc/scheduler/scheduler.h b/cc/scheduler/scheduler.h
index f6dd2bcf4ec36063c21d5fa380864d51db59eef8..64723d2899e22556136a847c54e7a80065e3653e 100644
--- a/cc/scheduler/scheduler.h
+++ b/cc/scheduler/scheduler.h
@@ -154,7 +154,7 @@ class CC_EXPORT Scheduler {
   class CC_EXPORT SyntheticBeginFrameSource : public TimeSourceClient {
    public:
     SyntheticBeginFrameSource(Scheduler* scheduler,
-                              base::SingleThreadTaskRunner* task_runner);
+                              scoped_refptr<DelayBasedTimeSource> time_source);
     virtual ~SyntheticBeginFrameSource();
 
     // Updates the phase and frequency of the timer.
@@ -186,6 +186,8 @@ class CC_EXPORT Scheduler {
       int layer_tree_host_id,
       const scoped_refptr<base::SingleThreadTaskRunner>& impl_task_runner);
 
+  virtual base::TimeTicks Now() const;
+
   const SchedulerSettings settings_;
   SchedulerClient* client_;
   int layer_tree_host_id_;