Comment by [email protected]: @micah: Both of the cases you describe are completely safe. To be precise, the *only* type of circular reference that will create a leak (on IE) is one that involves both Java[script] objects and native (COM) objects (usually Element, Window, and the like). Using the GWT libraries, there is generally no way to create such a leak without dropping to native Javascript code.
If you're seeing leaks in non-ancient versions of Gecko- and Webkit-based browsers, there are only two possibilities I'm aware of: 1. It's a traditional Java "pseudo-leak" (i.e., objects that accumulate in static collections and such), or 2. These browsers have created new memory leak patterns that I'm unware of. I would investigate (1) first. For more information: http://code.google.com/p/google-web-toolkit/wiki/DomEventsAndMemoryLeaks -- http://groups.google.com/group/Google-Web-Toolkit-Contributors
