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 3653c30cb014e0cce4e6d1c253eef9cc0d9c0ff2..3d0e045b6a6bf8f2186ea712076da91c06a55a54 100644
--- a/cc/scheduler/scheduler.h
+++ b/cc/scheduler/scheduler.h
@@ -18,6 +18,7 @@
 #include "cc/scheduler/draw_result.h"
 #include "cc/scheduler/scheduler_settings.h"
 #include "cc/scheduler/scheduler_state_machine.h"
+#include "ui/gfx/frame_time.h"
 
 namespace base {
 class SingleThreadTaskRunner;
@@ -144,7 +145,7 @@ 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.
@@ -176,6 +177,8 @@ 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_;