GWT 2.0 includes several new tools, the most significant of which is Speed Tracer, a Google Chrome extension that allows developers to profile Web app performance and identify sources of slowness.
But now, says Google product manager Andrew Bowers, HTML and CSS code often lead to performance bottlenecks.
Speed Tracer, he said, "allows you to profile the application over time and see what's going on."
The project's goal, he says, was to make a tool not just for profiling but for understanding, so developers aren't left trying to sort through massive dumps of performance data.
According to Bruce Johnson, the project's technical lead, Speed Tracer has helped accelerate some Web apps by a factor of 3x to 5x.
In addition, GWT includes an improved way to build interface code called UiBinder, which provides separates visual code elements from application logic.
Other refinements are discussed on the Google Web Toolkit blog.