Use TIMER_SLACK_MAXIMUM on the TaskScheduler service thread.

base/task_scheduler/post_task.h

Index: base/task_scheduler/post_task.h
diff --git a/base/task_scheduler/post_task.h b/base/task_scheduler/post_task.h
index 346a232147651683f9c5182d94e3fa155f3d458d..d6754b3f42fdb702d878bcac9587a8ee2859b882 100644
--- a/base/task_scheduler/post_task.h
+++ b/base/task_scheduler/post_task.h
@@ -86,6 +86,10 @@ BASE_EXPORT void PostTaskWithTraitsAndReply(
     const Closure& task,
     const Closure& reply);
 
+// Delayed tasks posted to TaskRunners returned by the functions below may be
+// coalesced (i.e. delays may be adjusted to reduce the number of wakeups and
+// hence power consumption).
+
 // Returns a TaskRunner whose PostTask invocations result in scheduling tasks
 // using |traits|. Tasks may run in any order and in parallel.
 BASE_EXPORT scoped_refptr<TaskRunner> CreateTaskRunnerWithTraits(