Media Controls: Re-create the play button

As per steimel@'s comment in crrev.com/c/991293 we should always
create the play button as we use it when the video element is
very small.

BUG=821961,821414

Change-Id: Icec781d0cd49529c72dd21c88d54727e81236890
Reviewed-on: https://chromium-review.googlesource.com/1000722
Commit-Queue: Becca Hughes <beccahughes@chromium.org>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Cr-Commit-Position: refs/heads/master@{#549266}

third_party/blink/renderer/modules/media_controls/media_controls_impl.cc

@@ -601,13 +601,7 @@ void MediaControlsImpl::PopulatePanel() {
     button_panel = media_button_panel_;
   }
 
-  // The play button should only be on the button panel if we are playing audio
-  // only or are using the legacy controls.
-  if (!IsModern() || is_acting_as_audio_controls_ ||
-      MediaElement().IsHTMLAudioElement()) {
-    button_panel->ParserAppendChild(play_button_);
-  }
-
+  button_panel->ParserAppendChild(play_button_);
   button_panel->ParserAppendChild(current_time_display_);
   button_panel->ParserAppendChild(duration_display_);