Currently, for each section (top-level of an engine, or the applies to section) of the new configuration (engines.json) we entries similar to:

{
  "webExtensionId": "foo@search.mozilla.org",
  "webExtensionVersion": "1.0",
  "webExtensionLocale": "ab",
}

The schema calls for:

{
  "webExtension": {
    "id": "foo@search.mozilla.org",
    "version": "1.0",
    "locale": "ab",
  }
}

I think we should change the code to match the schema because:

• This means the WebExtension section is grouped together visually, making it easier to read.
• There's less duplication of webExtension.
• It is easier for the schema to provide a re-usable webExtension object definition that is used in multiple places.
• It is better for display on the remote settings server, as we automatically get the webExtension grouped into a section nicely.

The one downside I recall from what Dale said, is that we'd need to write an object overriding mechanism in the search engine selector to take account of when an applies-to section overrides (maybe partially) the top level webExtension object.

I still think this would be worth it though, for the reasons above.

https://hg.mozilla.org/mozilla-central/rev/1e8a2884d6bf