Why debugging GWT is incredibly slow under Chrome, whereas the speed is reasonable under Firefox. (Firefox causes pain in its way as well. Since version 27 it doesn't even support GWT debugging plugin anymore.)
GWT debugging in Chrome has been slow for at least two years and it's not improving. So what is causing it and any solutions? I am also a web developer and I'm certain most cases Chrome is much faster and its Dev Tool is just awesome.
This is due to Chrome sandboxing plugins (so they don't have access to your computer's resources besides what Chromes allows), so passing things from the web page to the plugin (and back) is slower than in other browsers that run plugins in the same process (i.e. less securely).
That being said, Chrome will soon remove support for NPAPI plugins too, so DevMode won't work there either. Try SuperDevMode, and keep in mind it'll get a perf boost in GWT 2.7, to be released in a couple months.
