[GTK] Volume slider shows below the panel with videos in certain cases
https://bugs.webkit.org/show_bug.cgi?id=130608

Reviewed by Jer Noble.

Source/WebCore:

We need to delay the moment we check if the volume slider shows up
or down. If the video was not visible, the offsets were 0 and it
was forced to be shown below the panel.

Test: media/video-initially-hidden-volume-slider-up.html

* Modules/mediacontrols/mediaControlsApple.js:
(Controller.prototype.createControls): Moved volumebox pseudo from
the subclass. The test checks for it and it would fail in Mac.
* Modules/mediacontrols/mediaControlsGtk.js:
(ControllerGtk.prototype.createControls): Moved volumebox pseudo
to the superclass.
(ControllerGtk.prototype.handleMuteButtonMouseOver): Check if
volume slider should show up or down.
(ControllerGtk.prototype.updateReadyState): Removed check for
volume slider direction.

LayoutTests:

* media/video-initially-hidden-volume-slider-up-expected.txt: Added.
* media/video-initially-hidden-volume-slider-up.html: Added.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@166227 268f45cc-cd09-0410-ab3c-d52691b4dbfc