Hi,

I implemented some primitives to expose some WebKit user content APIs
(user script and script message handlers) for WebKit Xwidgets, both
for WebKitGTK impl and NS/mac impl.

The user script API makes it possible to reliable and predictable injecting
script into a Webkit Xwidget, which is useful for customizing the WebView
behavior.

The script message handler API makes it possible to trigger event in emacs
from JavaScript, and can be used to implement procedure calling from
js to elisp. Currently only the other way around is possible.

The patch is attached.

Best,
Qiantan

qhong@mit.edu