[Modern Media Controls] Playing an <audio> element on iOS makes the controls disappear

[Modern Media Controls] Playing an <audio> element on iOS makes the controls disappear
https://bugs.webkit.org/show_bug.cgi?id=168047
<rdar://problem/30441939>

Reviewed by Eric Carlson.

Source/WebCore:

The controls bar auto-hide behavior is disabled for <audio> elements, but on iOS we have
a TapGestureRecognizer to identify when controls are tapped to toggle controls visibility.
This gesture recognizer would be on at all times, but it should only be enabled when
fadesToIdle is set to true.

Test: media/modern-media-controls/media-controller/media-controller-ios-only-enable-tap-gesture-recognizer-with-fades-when-idle.html

* Modules/modern-media-controls/controls/controls-bar.js:
(ControlsBar.prototype.set fadesWhileIdle):

LayoutTests:

Add a new iOS-specific test that checks the TapGestureRecognizer is only enabled when
fadesToIdle is true.

* media/modern-media-controls/media-controller/media-controller-ios-only-enable-tap-gesture-recognizer-with-fades-when-idle-expected.txt: Added.
* media/modern-media-controls/media-controller/media-controller-ios-only-enable-tap-gesture-recognizer-with-fades-when-idle.html: Added.
* platform/mac/TestExpectations:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@211955 268f45cc-cd09-0410-ab3c-d52691b4dbfc