Bug#1149700: WebKit bug 322394

[Mark Williams]

This is WebKit bug 322394 — a regression from 317619@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@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