gecko-dev/toolkit/components/extensions/ext-runtime.js

const { classes: Cc, interfaces: Ci, utils: Cu } = Components;

Cu.import("resource://gre/modules/ExtensionUtils.jsm");
let {
  EventManager,
  ignoreEvent,
} = ExtensionUtils;

extensions.registerAPI((extension, context) => {
  return {
    runtime: {
      onStartup: new EventManager(context, "runtime.onStartup", fire => {
        extension.onStartup = fire;
        return () => {
          extension.onStartup = null;
        };
      }).api(),

      onInstalled: ignoreEvent(),

      onMessage: context.messenger.onMessage("runtime.onMessage"),

      onConnect: context.messenger.onConnect("runtime.onConnect"),

      sendMessage: function(...args) {
        let extensionId, message, options, responseCallback;
        if (args.length == 1) {
          message = args[0];
        } else if (args.length == 2) {
          [message, responseCallback] = args;
        } else {
          [extensionId, message, options, responseCallback] = args;
        }
        let recipient = {extensionId: extensionId ? extensionId : extension.id};
        return context.messenger.sendMessage(Services.cpmm, message, recipient, responseCallback);
      },

      getManifest() {
        return Cu.cloneInto(extension.manifest, context.cloneScope);
      },

      id: extension.id,

      getURL: function(url) {
        return extension.baseURI.resolve(url);
      },
    },
  };
});