First, SWT control for Browser is what DJ Native Swing is using, but it also has all sorts of glue code to make it thread safe with Swing. Thus, changing to pure SWT would yield the same problems, plus threading issues to solve.
About Google Chrome Frame in SWT, and thus in DJ Native Swing, there is currently no support in SWT itself. See this bug: https://bugs.eclipse.org/bugs/show_bug.cgi?id=317322
SWT, and DJ Native Swing, allow to create one's own ActiveX bridge. Maybe you could create your own component for Google Chrome Frame ActiveX on windows, similar to what DJ Native Swing does for the Windows Media Player component.