Media Controls: fix crash when actions and dismiss on oveflow are racing.

This doesn't fix the cause but only the crash because we will need to
send this to Beta. A proper fix will require some refactoring. It means
that M67 will probably have slightly different data for time to dismiss
and time to action.

Bug: 835748
Change-Id: Iec87eb0b05f07c54c3c292180a6a59a1aa35666d
Reviewed-on: https://chromium-review.googlesource.com/1034742Reviewed-by: Becca Hughes <beccahughes@chromium.org>
Commit-Queue: Mounir Lamouri <mlamouri@chromium.org>
Cr-Commit-Position: refs/heads/master@{#554792}

third_party/blink/renderer/modules/media_controls/elements/media_control_overflow_menu_list_element.cc

@@ -21,7 +21,11 @@ MediaControlOverflowMenuListElement::MediaControlOverflowMenuListElement(
 
 void MediaControlOverflowMenuListElement::MaybeRecordTimeTaken(
     TimeTakenHistogram histogram_name) {
-  DCHECK(time_shown_);
+  // TODO(mlamouri): we may end up hitting a race where both actions and dismiss
+  // are fired very close to eachother. This change is meant to prevent a crash
+  // but doesn't avoid the sometimes incorrect metrics recording.
+  if (!time_shown_)
+    return;
 
   if (current_task_handle_.IsActive())
     current_task_handle_.Cancel();