Example Shield Study Embedded Web Extension

install

npm install npm run build

at second shell/prompt, watch files for changes to rebuild:

npm run watch

in Firefox:

1. about:debugging > [load temporary addon] > choose dist/addon.xpi`
2. tools > Web Developer > Browser Toolbox

Effects:

1. See a new button (with a 'puzzle piece') symbol.
2. to end early: Click on button multiple times until the 'too-popular' endpoint is reached.

Further extensions / modifications

1. (TBD)

Description of architecture

Embedded Web Extension (/webextension/) lives inside a restartless (bootstrap.js) extension.

During bootstrap.js:startup(data, reason):

a. `shieldUtils` imports and sets configuration from `Config.jsm`
b. `bootstrap.js:chooseVariation` explicitly and deterministically chooses a variation from `studyConfig.weightedVariations`
c.  the WebExtension starts up
d.  `boostrap.js` listens for requests from the `webExtension` that are study related:  `["info", "telemetry", "endStudy"]`
e.  `webExtension` (`background.js`) asks for `info` from `studyUtils` using `askShield` function.
f.  Feature starts using the `variation` from that info.
g.  Feature instruments user button to send `telemetry` and to `endStudy` if the button is clicked enough.