[MessageLoop] Don't clobber |recent_time_|

I'm about to duplicate that line in
https://chromium-review.googlesource.com/c/chromium/src/+/1106434
and it feels silly to clobber |recent_time_| since TimeTicks is
monotically increasing regardless of nested loops (cloberring it is at
best irrelevant and at worse forces an unecessary recomputation of
Now()).

R=danakj@chromium.org, kylechar@chromium.org

Bug: None
Change-Id: Ia11ca15fcde850fba5cc33bc1cbac68386495719
Reviewed-on: https://chromium-review.googlesource.com/1125168Reviewed-by: kylechar <kylechar@chromium.org>
Reviewed-by: danakj <danakj@chromium.org>
Commit-Queue: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#572592}

base/message_loop/message_loop.cc

@@ -428,7 +428,7 @@ bool MessageLoop::DoWork() {
 bool MessageLoop::DoDelayedWork(TimeTicks* next_delayed_work_time) {
   if (!task_execution_allowed_ ||
       !incoming_task_queue_->delayed_tasks().HasTasks()) {
-    recent_time_ = *next_delayed_work_time = TimeTicks();
+    *next_delayed_work_time = TimeTicks();
 
     // It's possible to be woken up by a system event and have it cancel the
     // upcoming delayed task from under us before DoDelayedWork() -- see comment