Replace HeapListHashSet with HeapLinkedHashSet in MediaControlsTouchlessMediaEventListener

ListHashSet is deprecated in favor of LinkedHashSet.

HeapLinkedHashSet's invalidate iterators when the container is
modified.  This does not happen in this usage, so replacement is
simple.

Bug: 614112
Change-Id: I33452c4957e20babb222e6e0257cfd119e861896
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1639725Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Commit-Queue: Abhijeet Kandalkar <abhijeet@igalia.com>
Cr-Commit-Position: refs/heads/master@{#665815}

third_party/blink/renderer/modules/media_controls/touchless/media_controls_touchless_media_event_listener.h

@@ -29,7 +29,7 @@ class MediaControlsTouchlessMediaEventListener final
  private:
   HTMLMediaElement& GetMediaElement();
 
-  HeapListHashSet<Member<MediaControlsTouchlessMediaEventListenerObserver>>
+  HeapLinkedHashSet<Member<MediaControlsTouchlessMediaEventListenerObserver>>
       observers_;
   Member<HTMLMediaElement> media_element_;