cc: Cleanup DelayBasedTimeSource code.

cc/scheduler/delay_based_time_source.cc

Index: cc/scheduler/delay_based_time_source.cc
diff --git a/cc/scheduler/delay_based_time_source.cc b/cc/scheduler/delay_based_time_source.cc
index b1f68bd27c94fda46cd5919eed1a76326feeeedb..55a804a4454de62c7e39e3785487149ac6b0441e 100644
--- a/cc/scheduler/delay_based_time_source.cc
+++ b/cc/scheduler/delay_based_time_source.cc
@@ -63,7 +63,11 @@ base::TimeTicks DelayBasedTimeSource::SetActive(bool active) {
     return base::TimeTicks();
   }
 
-  PostNextTickTask(Now());
+  base::TimeTicks now = Now();
+  PostNextTickTask(now);
+
+  if (current_parameters_.tick_target <= now)
+    return base::TimeTicks();
 
   // Determine if there was a tick that was missed while not active.
   base::TimeTicks last_tick_time_if_always_active =
@@ -227,11 +231,10 @@ base::TimeTicks DelayBasedTimeSource::NextTickTarget(base::TimeTicks now) {
 
 void DelayBasedTimeSource::PostNextTickTask(base::TimeTicks now) {
   base::TimeTicks new_tick_target = NextTickTarget(now);
+  DCHECK(new_tick_target >= now);

[brianderson, 2015/06/23 21:00:29]

DCHECK_GE

 
   // Post another task *before* the tick and update state
-  base::TimeDelta delay;
-  if (now <= new_tick_target)

[brianderson, 2015/06/23 21:00:29]

I forget why this was needed. Could small jitter in the timebase cause this
condition to hit?

[sunnyps, 2015/06/26 00:45:28]

This condition should always be true. See the DCHECK above.

-    delay = new_tick_target - now;
+  base::TimeDelta delay = new_tick_target - now;
   task_runner_->PostDelayedTask(FROM_HERE,
                                 base::Bind(&DelayBasedTimeSource::OnTimerFired,
                                            weak_factory_.GetWeakPtr()),