Some media/track tests fail or assert on Mac
https://bugs.webkit.org/show_bug.cgi?id=97132

Reviewed by Simon Fraser.

Source/WebCore:

Rationalize the font and padding behavior of cues and cue boxes; ::cue pseudo elements cannot have padding
values applied via CSS (due to padding not being included in the whitelist of applicable CSS properties).
Also, the font values were being applied to the box at one level and the cue at another, leading to incorrect
layout in the snapToLines case. Padding has been removed from the cue, and the font settings are now applied
to the box exclusively.

Additionally, a few drive-by changes were made in TextTrackCue to the return values of displayTreeInternal() &
element(), which previously returned a PassRefPtr<> instead of a plain pointer.

* css/mediaControls.css:
(video::-webkit-media-text-track-container): Move the font size to the display selector.
(video::cue): Remove the display:inline and padding:2px declarations.
(video::-webkit-media-text-track-display): Remove the -webkit-line-content now that the ::cue has no padding.
* html/track/TextTrackCue.cpp:
(WebCore::TextTrackCue::TextTrackCue): The background box is now a span, rather than a forced-inline div.
(WebCore::TextTrackCue::displayTreeInternal): Return a plain pointer.
(WebCore::TextTrackCue::getDisplayTree): Ditto.
(WebCore::TextTrackCue::setFontSize): Set the font on the box, not the cue.
* html/track/TextTrackCue.h:
(WebCore::TextTrackCue::element): Return a plain pointer.
* html/track/TextTrackCueGeneric.cpp:
(WebCore::TextTrackCueGenericBoxElement::applyCSSProperties): The cue element is now a span, not a div.
* page/CaptionUserPreferencesMac.mm:
(WebCore::CaptionUserPreferencesMac::captionsWindowCSS): Whitespace.
(WebCore::CaptionUserPreferencesMac::captionsBackgroundCSS): Do not set padding on the cue.

LayoutTests:

* media/track/captions-webvtt/captions-snap-to-lines-not-set.vtt:
* media/track/track-cue-rendering-horizontal.html:
* media/track/track-cue-rendering-snap-to-lines-not-set-expected.txt:
* media/track/track-cue-rendering-snap-to-lines-not-set.html:
* media/track/track-cue-rendering-vertical.html:
* platform/mac/TestExpectations:
* platform/mac/media/track/track-cue-rendering-horizontal-expected.png:
* platform/mac/media/track/track-cue-rendering-horizontal-expected.txt:
* platform/mac/media/track/track-cue-rendering-vertical-expected.png:
* platform/mac/media/track/track-cue-rendering-vertical-expected.txt:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@150260 268f45cc-cd09-0410-ab3c-d52691b4dbfc