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 ce3fed783bf8de1012ee2aa40795227f5769b63e..b6fc979ff6db708db0e76c19c48651ef0be477ea 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.
@@ -185,6 +185,8 @@ class CC_EXPORT Scheduler {
             int layer_tree_host_id,
             const scoped_refptr<base::SingleThreadTaskRunner>& task_runner);
 
+  virtual base::TimeTicks Now() const;
+
   const SchedulerSettings settings_;
   SchedulerClient* client_;
   int layer_tree_host_id_;