function onContentAvailable(content)
        {
            var contentEncoded = false;
            if (contentProvider instanceof WebInspector.Resource)
                contentEncoded = contentProvider.contentEncoded;
            if (contentProvider instanceof WebInspector.NetworkRequest)
                contentEncoded = contentProvider.contentEncoded;
            var response = {
                encoding: contentEncoded && content ? "base64" : "",
                content: content
            };
            this._dispatchCallback(message.requestId, port, response);
        }
@param {?string} content
@this {WebInspector.ExtensionServer}