Switch to native Promises and fetch

For fetch and AbortController we provide native polyfills (see
resources/src/skip-web2017-polyfills.js) so safe to use this here.
This will be empty for modern browsers.

Change-Id: Ic0f55eb0a0276be3587a4b866834bddff1124ad2

.nycrc.json

@@ -13,9 +13,9 @@
 	"include": [ "src/**/*.js" ],
 
 	"//": "Set the coverage percentage by category thresholds.",
-	"statements": 83,
+	"statements": 80,
 	"branches": 70,
-	"functions": 82,
+	"functions": 80,
 	"lines": 90,
 
 	"//": "Fail if the coverage is below threshold.",

extension.json

@@ -222,6 +222,7 @@
 				"popups-refpreview-collapsible-placeholder"
 			],
 			"dependencies": [
+				"web2017-polyfills",
 				"ext.popups.icons",
 				"ext.popups.images",
 				"mediawiki.experiments",

package.json

@@ -71,7 +71,7 @@
 	"bundlesize": [
 		{
 			"path": "resources/dist/index.js",
-			"maxSize": "13.5kB"
+			"maxSize": "14.0kB"
 		}
 	]
 }

src/actions.js

@@ -162,11 +162,11 @@ export function fetch( gateway, title, el, token, type ) {
 				throw exception;
 			} );
 
-		return $.when(
+		return Promise.all( [
 			chain,
 			wait( getDwellDelay( type ) )
-		)
-			.then( ( result ) => {
+		] )
+			.then( ( [ result ] ) => {
 				dispatch( {
 					type: types.FETCH_COMPLETE,
 					el,

src/gateway/page.js

@@ -6,6 +6,26 @@ import constants from '../constants';
 import createMediaWikiApiGateway from './mediawiki';
 import createRESTBaseGateway from './rest';
 import * as formatters from './restFormatters';
+import { abortablePromise } from './index.js';
+
+/**
+ * @param {Object} options
+ * @return {Promise}
+ */
+function ajax( options ) {
+	const controller = new AbortController();
+	const signal = controller.signal;
+
+	return abortablePromise(
+		fetch( options.url, {
+			headers: options.headers,
+			signal
+		} ).then( ( resp ) => resp.json() ),
+		() => {
+			controller.abort();
+		}
+	);
+}
 
 /**
  * Creates a page preview gateway with sensible values for the dependencies.
@@ -25,10 +45,10 @@ export default function createPagePreviewGateway( config ) {
 			return createMediaWikiApiGateway( new mw.Api(), gatewayConfig );
 		case 'restbasePlain':
 			return createRESTBaseGateway(
-				$.ajax, restConfig, formatters.parsePlainTextResponse );
+				ajax, restConfig, formatters.parsePlainTextResponse );
 		case 'restbaseHTML':
 			return createRESTBaseGateway(
-				$.ajax, restConfig, formatters.parseHTMLResponse );
+				ajax, restConfig, formatters.parseHTMLResponse );
 		default:
 			throw new Error( 'Unknown gateway' );
 	}

webpack.config.js

@@ -112,8 +112,8 @@ module.exports = ( env, argv ) => ( {
 		// Minified uncompressed size limits for chunks / assets and entrypoints. Keep these numbers
 		// up-to-date and rounded to the nearest 10th of a kibibyte so that code sizing costs are
 		// well understood. Related to bundlesize minified, gzipped compressed file size tests.
-		maxAssetSize: 42.5 * 1024,
-		maxEntrypointSize: 42.5 * 1024,
+		maxAssetSize: 42.9 * 1024,
+		maxEntrypointSize: 42.9 * 1024,
 
 		// The default filter excludes map files but we rename ours.
 		assetFilter: ( filename ) => !filename.endsWith( srcMapExt )