I have been developing Eclipse plugins for more than four years now. I have implemented many features in the ColdFusion Builder, which is an Eclipse based IDE. Eclipse SDK provides a SWT Browser control which can be used within Eclipse plugin to display HTML files. Eclipse does not include any browser, but it uses the system browser- on Windows it is Internet Explorer and on Macintosh it is Safari. I have used this control mainly to display static HTML content or open a URL on a remote server, e.g. for executing ColdFusion Builder extensions written in CFML.
You then need to associate this function with the browser control, for example -
You might find this somewhat similar to Adobe AIR. Of course AIR has a lot more features than this simple application that I am creating – but one aspect of AIR, which is easily converting web application to desktop application is same in the Eclipse RCP application I am developing.