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 97b17b7283aaf4e357be4fd8e5726298f80c63cf..70522eb218621d629dc4bcf14f445c50c97397c6 100644
--- a/cc/scheduler/scheduler.h
+++ b/cc/scheduler/scheduler.h
@@ -137,7 +137,7 @@ 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.
@@ -168,6 +168,8 @@ 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_;
@@ -198,6 +200,8 @@ class CC_EXPORT Scheduler {
   bool inside_process_scheduled_actions_;
   SchedulerStateMachine::Action inside_action_;
 
+  base::TimeDelta VSyncInterval() { return vsync_interval_; }
+
  private:
   base::TimeTicks AdjustedBeginImplFrameDeadline(
       const BeginFrameArgs& args,
@@ -221,8 +225,6 @@ class CC_EXPORT Scheduler {
   void PollForAnticipatedDrawTriggers();
   void PollToAdvanceCommitState();
 
-  base::TimeDelta VSyncInterval() { return vsync_interval_; }
-
   base::TimeDelta EstimatedParentDrawTime() {
     return estimated_parent_draw_time_;
   }