Fixing and enhancing OrderedSimpleTaskRunner to allow 100% deterministic tests.

cc/scheduler/scheduler.cc

Index: cc/scheduler/scheduler.cc
diff --git a/cc/scheduler/scheduler.cc b/cc/scheduler/scheduler.cc
index 52e0f9e093e4dc560c7af23768ef568caf0e9f3b..f0468f0a85f72ecbebd36a429252f7a45bdddd3f 100644
--- a/cc/scheduler/scheduler.cc
+++ b/cc/scheduler/scheduler.cc
@@ -12,7 +12,6 @@
 #include "cc/debug/devtools_instrumentation.h"
 #include "cc/debug/traced_value.h"
 #include "cc/scheduler/delay_based_time_source.h"
-#include "ui/gfx/frame_time.h"
 
 namespace cc {
 
@@ -129,6 +128,10 @@ void Scheduler::SetupSyntheticBeginFrames() {
       new SyntheticBeginFrameSource(this, impl_task_runner_.get()));
 }
 
+base::TimeTicks Scheduler::Now() const {
+  return gfx::FrameTime::Now();
+}
+
 void Scheduler::CommitVSyncParameters(base::TimeTicks timebase,
                                       base::TimeDelta interval) {
   // TODO(brianderson): We should not be receiving 0 intervals.
@@ -260,7 +263,7 @@ base::TimeTicks Scheduler::AnticipatedDrawTime() const {
       begin_impl_frame_args_.interval <= base::TimeDelta())
     return base::TimeTicks();
 
-  base::TimeTicks now = gfx::FrameTime::Now();
+  base::TimeTicks now = Now();
   base::TimeTicks timebase = std::max(begin_impl_frame_args_.frame_time,
                                       begin_impl_frame_args_.deadline);
   int64 intervals = 1 + ((now - timebase) / begin_impl_frame_args_.interval);
@@ -335,7 +338,7 @@ void Scheduler::BeginUnthrottledFrame() {
   DCHECK(!settings_.throttle_frame_production);
   DCHECK(begin_retro_frame_args_.empty());
 
-  base::TimeTicks now = gfx::FrameTime::Now();
+  base::TimeTicks now = Now();
   base::TimeTicks deadline = now + vsync_interval_;
 
   BeginFrameArgs begin_frame_args =
@@ -446,7 +449,7 @@ void Scheduler::BeginRetroFrame() {
   // TODO(brianderson): In the future, long deadlines could result in us not
   // draining the queue if we don't catch up. If we consistently can't catch
   // up, our fallback should be to lower our frame rate.
-  base::TimeTicks now = gfx::FrameTime::Now();
+  base::TimeTicks now = Now();
   base::TimeDelta draw_duration_estimate = client_->DrawDurationEstimate();
   while (!begin_retro_frame_args_.empty() &&
          now > AdjustedBeginImplFrameDeadline(begin_retro_frame_args_.front(),
@@ -562,7 +565,7 @@ void Scheduler::ScheduleBeginImplFrameDeadline(base::TimeTicks deadline) {
   begin_impl_frame_deadline_task_.Cancel();
   begin_impl_frame_deadline_task_.Reset(begin_impl_frame_deadline_closure_);
 
-  base::TimeDelta delta = deadline - gfx::FrameTime::Now();
+  base::TimeDelta delta = deadline - Now();
   if (delta <= base::TimeDelta())
     delta = base::TimeDelta();
   impl_task_runner_->PostDelayedTask(