function handleGetFile(file, text) {
    var next = fileCallBacks[file];
    if (next) {
        try {
            next(null, text);
        } catch (e) {
            _reportError(e, file);
        }
    }
    delete fileCallBacks[file];
}
Handle a response from the main thread providing the contents of a file
@param {string} file - the name of the file
@param {string} text - the contents of the file