Bug#1149700: WebKit bug 322394

[Mark Williams]

This is WebKit bug 322394 — a regression from 317619 at main, which made 
WebKit require the process's OS main thread to be the first to call 
initializeMainThread(). SWT initializes WebKit from the GTK UI thread 
the JVM creates, so the RELEASE_ASSERT in MainThread.cpp:47 always fails.

Reverted upstream in 321625 at main. Fedora shipped it downstream as 
webkitgtk-2.54.0-2.fc45 rather than waiting for 2.54.1, which fixed 
Eclipse there while keeping the 2.54.0 security fixes.

https://bugs.webkit.org/show_bug.cgi?id=322394