WKView is setting itself as the window's _growBoxOwner in an override of _updateGrowBoxForWindowFrameChange, but isn't clearing it at any point. NSWindow doesn't retain/release its growBoxOwner, so this can lead to a bad object ref in NSWindow that results in crashes.
Created attachment 86069 [details] Patch to clear growBoxOwner at the appropriate time.
Committed in http://trac.webkit.org/changeset/81372