Google released a new Chrome Developer Plugin for Mac and Linux users. "In addition to new OS support, there's an important security fix included in this update. You'll see GWT icon appear in your browser bar when the plugin sees the ?gwt.codesvr fragment in a URL, and it'll turn black and white if you need to authorize that host. If you see a full-color icon, that indicates your permissions are in order. You can click the icon to quick-jump to the permissions configuration," explains Google.
Note to Windows users: "we've created a new permissions UI baked into the extension rather than using native Windows dialogs. You'll need to re-add any hosts you had configured for this new version."
To download and install the new plugin, simply start debugging your GWT app and point Chrome at the URL provided by the Google Plugin for Eclipse. From there you'll be prompted to install the "GWT Developer Plugin for Chrome". Or, simply browse directly here.