patch updated with some mac build fixups and the public key is now embedded in the manifest so that packed/unpacked use the same well known URI for the background page.
http://gwt-code-reviews.appspot.com/1084801/diff/28001/29022 File plugins/npapi/manifest-template.json (right): http://gwt-code-reviews.appspot.com/1084801/diff/28001/29022#newcode13 plugins/npapi/manifest-template.json:13: "key": "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDi6RrEy9YllRLM8bGBcIEk5ECAG2z+8ngTz7wwzRAQJpOzDp1Alq8fQFjH0+dzxok4RFLrWKHjxGqvXzWyWyTEo2nY3ScHLN/RoANMs8pl9X6TygRyO+3naqZOtLCrYHfV49JKXnYoFVbY5eBVYxHYY3BHAOKJj9onyAM4UPmMzQIDAQAB", note, this is the public key. since the extension URI is derived from the signature, embedding the public key here lets any user develop and load the unpacked version without having the actual key. we use this same trick in speedtracer. http://gwt-code-reviews.appspot.com/1084801/show -- http://groups.google.com/group/Google-Web-Toolkit-Contributors