Chrome Boosters are third-party modules that can be used to provide functionality to Jetpack Features or Firefox Add-ons. As their name implies, they are chrome-privileged and use dependency injection to offer functionality to non-chrome-privileged Jetpacks.

These modules essentially formalize the mechanism used within Jetpack to provide the jetpack namespace to Jetpacks.

Chrome Boosters have the following characteristics:

They are a superset of the SecurableModule standard.
They can be loaded and unloaded multiple times throughout the lifetime of their containing application (yes, leaks are an unfortunate possibility).
They have access to an onUnload() function that allows them to register callbacks to perform cleanup tasks when unloaded.
They have full access to XPConnect's Components object, and all its sub-objects.

For security purposes, Chrome Boosters can only be accessed either

locally, through a containing addon, or
over secure HTTP to a trusted host.

Additionally, to encourage good coding practices and documentation, Chrome Boosters must have:

A simple, straightforward mechanism for writing and executing test cases.
An easy-to-learn documentation system capable of producing beautiful documentation.
A mechanism for tracking objects of interest belonging to the Chrome Booster to aid in memory profiling and leak detection.

Potential Code

This code doesn't actually work; it's just aspirational.

Assume that the following code is contained in a file at chrome://some_extension/content/foo.html.

<html>
<!-- This script makes the SecurableModule global available. -->
<script src="securable-module.js"></script>
<script>
// Create a loader for SecurableModules that gives them chrome
// privileges by default and roots the filesystem at (our URL)/lib.
var loader = SecurableModule.Loader({defaultPrincipal: "system",
                                     rootPath: "lib"});

// Load the 'foo' SecurableModule and call its exported doSomething()
// function.
loader.require('blarg').doSomething();

window.addEventListener(
  "unload",
  function() {
    // Send an unload signal to free any resources created by modules so
    // far.
    loader.require('unload').send();
  },
  false
);
</script>
</html>

Note that the unload module conventions are laid out by the Narwhal CommonJS-based platform.

Labs/Jetpack/JEP/25

Potential Code