Update processDocuments() signature for allow passing headers

Also:

- Actually use the cookie sandbox passed to processDocuments()

For zotero/translation-server#16, we want to include Accept-Language
(and maybe other headers) from the client request in upstream requests,
which requires passing it to both non-translate processDocuments().
translation-server's non-translate processDocuments() is defined in that
repo, but it's called by the cross-repo translate processDocuments() in
utilities_translate.js, so the signature needs to be changed in both
repos.

We also apparently weren't using the cookieSandbox in client
processDocuments() calls, though I think that only would've affected
translator testing.

chrome/content/zotero/tools/testTranslators/translatorTester.js

@@ -421,7 +421,9 @@ Zotero_TranslatorTester.prototype.fetchPageAndRunTest = function (test, testDone
 				testDoneCallback(obj, test, status, message);
 			});
 		},
-		this._cookieSandbox,
+		{
+			cookieSandbox: this._cookieSandbox
+		}
 	)
 	.catch(function (e) {
 		testDoneCallback(this, test, "failed", "Translation failed to initialize: " + e);

chrome/content/zotero/xpcom/http.js

@@ -903,10 +903,12 @@ Zotero.HTTP = new function() {
 	 * @param {String|String[]} urls URL(s) of documents to load
 	 * @param {Function} processor - Callback to be executed for each document loaded; if function returns
 	 *     a promise, it's waited for before continuing
-	 * @param {Zotero.CookieSandbox} [cookieSandbox] Cookie sandbox object
+	 * @param {Object} [options]
+	 * @param {Zotero.CookieSandbox} [options.cookieSandbox] - Cookie sandbox object
+	 * @param {Object} [options.headers] - Headers to include in the request
 	 * @return {Promise<Array>} - A promise for an array of results from the processor runs
 	 */
-	this.processDocuments = async function (urls, processor, cookieSandbox) {
+	this.processDocuments = async function (urls, processor, options = {}) {
 		// Handle old signature: urls, processor, onDone, onError, dontDelete, cookieSandbox
 		if (arguments.length > 3) {
 			Zotero.debug("Zotero.HTTP.processDocuments() now takes only 3 arguments -- update your code");
@@ -914,6 +916,14 @@ Zotero.HTTP = new function() {
 			var onError = arguments[3];
 			var cookieSandbox = arguments[5];
 		}
+		else if (options instanceof Zotero.CookieSandbox) {
+			Zotero.debug("Zotero.HTTP.processDocuments() now takes an 'options' object for its third parameter -- update your code");
+			var cookieSandbox = options;
+		}
+		else {
+			var cookieSandbox = options.cookieSandbox;
+			var headers = options.headers;
+		}
 		
 		if (typeof urls == "string") urls = [urls];
 		var funcs = urls.map(url => () => {
@@ -921,7 +931,9 @@ Zotero.HTTP = new function() {
 				"GET",
 				url,
 				{
-					responseType: 'document'
+					responseType: 'document',
+					cookieSandbox,
+					headers
 				}
 			)
 			.then((xhr) => {

chrome/content/zotero/xpcom/utilities_translate.js

@@ -261,7 +261,9 @@ Zotero.Utilities.Translate.prototype.processDocuments = async function (urls, pr
 					if (!processor) return;
 					return processDoc(doc);
 				},
-				translate.cookieSandbox
+				{
+					cookieSandbox: translate.cookieSandbox
+				}
 			)
 		);
 	}