GetTimeToCallback() returns estimated time to callback.

base/timer/timer.h

Index: base/timer/timer.h
diff --git a/base/timer/timer.h b/base/timer/timer.h
index 50aedbd4cec28e97c408b2acd8b896c70526732c..64b340a64bc5cef63bc5430c6a0f097bac65fce0 100644
--- a/base/timer/timer.h
+++ b/base/timer/timer.h
@@ -100,6 +100,11 @@ class BASE_EXPORT Timer {
   // Returns the current delay for this timer.
   virtual TimeDelta GetCurrentDelay() const;
 
+  // Returns an estimated time to the timer calling  the user_task_ back. If

[Mark Mentovai, 2016/12/06 18:01:16]

Two spaces between “calling” and “the” should only be one. And add to this
comment that the function may return a negative TimeDelta.

[The one and only Dr. Crash, 2016/12/06 20:04:38]

Can it return a negative TimeDelta? If the timer isn't running (which will
happens automatically for a one shot timer, for example), it will return
TimeDelta::Max(). If it is running, then it should always be positive.

[Mark Mentovai, 2016/12/06 20:09:53]

If things get jammed up and the callback should have fired already but hasn’t
had a chance to run, the delta will be negative.

+  // the timer is not running or if user_task_ is not set, return
+  // TimeDelta::Max().
+  virtual TimeDelta GetTimeToCallback() const;

[Mark Mentovai, 2016/12/06 18:01:16]

No point in making this virtual if nobody overrides it.

[The one and only Dr. Crash, 2016/12/06 20:04:38]

Ok. As far as I could tell, other virtual functions (e.g. GetCurrentDelay())
aren't overriden either.

+
   // Set the task runner on which the task should be scheduled. This method can
   // only be called before any tasks have been scheduled. The task runner must
   // run tasks on the same thread the timer is used on.