Google on Thursday revealed Chrome 2.0, a purportedly faster and more feature-filled version of the search giant’s Web browser. The extra speed comes from an update to its V8 JavaScript engine and from a new version of the open source WebKit rendering engine. However, Chrome’s speed advantage may soon be overshadowed by rivals. Mozilla, for example, is expected to release a final version of Firefox 3.5. Also, speeding up JavaScript may lead to security problems.