A new IDE for developing Chrome apps has been shown off by Google and is available for you to use.
Chrome Dev Editor is currently a Developer Preview that is open sourced under Apache 2.0. Under the covers it’s a Chrome app written in Dart and uses Polymer for many of its UI elements. It uses Ace as its code editor, so has features such as syntax highlighting.
According to the FAQ about it on GitHub, the fact it’s a Chrome App means it can use some native capabilities such as raw filesystem access for writing folders on disk and USB access to communicate with mobile devices. You install CDE once and it gets synced across all your computers where you’re signed in to Chrome.
You can test apps using CDE’s local webserver, and once the app is working, can deploy from CDE directly to the Chrome Web Store or an Android mobile device.