Move inheriting method to the superclass in the JavaScript media controls
https://bugs.webkit.org/show_bug.cgi?id=128897

Reviewed by Jer Noble.

The inheriting method of the JavaScript multimedia controls was
moved from the subclasses to the superclass because this way it is
only defined once.

* Modules/mediacontrols/mediaControlsApple.js:
(Controller.prototype.extend): Added to replace inheritFrom in the
subclasses.
* Modules/mediacontrols/mediaControlsGtk.js:
* Modules/mediacontrols/mediaControlsiOS.js: Removed inheritFrom
and used extend.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@164279 268f45cc-cd09-0410-ab3c-d52691b4dbfc