[Chromium] Seperate GTK specific Gyp rules from X11 Gyp rules

[Chromium] Seperate GTK specific Gyp rules from X11 Gyp rules
https://bugs.webkit.org/show_bug.cgi?id=68936

Reviewed by Tony Chang.

Source/WebCore:

Chromium need to be built without Gtk for future version of ChromiumOS.

* WebCore.gyp/WebCore.gyp:

Source/WebKit/chromium:

* WebKit.gyp:
* public/gtk/WebFontInfo.h:
* public/linux/WebFontInfo.h: Copied from Source/WebKit/chromium/public/gtk/WebFontInfo.h.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@96233 268f45cc-cd09-0410-ab3c-d52691b4dbfc