[iOS Media] Audio should hide timeline scrubber until playback starts

[iOS Media] Audio should hide timeline scrubber until playback starts
https://bugs.webkit.org/show_bug.cgi?id=141542
<rdar://problem/19820685>

Reviewed by Eric Carlson.

We regressed from the system behaviour in iOS 7, where the timeline
scrubber for an audio element is not shown until the user starts
playback.

* Modules/mediacontrols/mediaControlsiOS.css:
(video::-webkit-media-controls-panel): Fix the alignment of the flexbox.
(audio::-webkit-media-controls-status-display): Add the style for the status display.
* Modules/mediacontrols/mediaControlsiOS.js:
(ControllerIOS.prototype.configureInlineControls): Start hidden if we are an <audio>.
(ControllerIOS.prototype.configureFullScreenControls): Drive by comment change.
(ControllerIOS.prototype.setPlaying): Unhide the timeline.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@180024 268f45cc-cd09-0410-ab3c-d52691b4dbfc