Cancel snapshot saves after 15 seconds

Otherwise a save could go on forever and the connector will never show
an error, and if you quit Zotero the connector will show the
save-to-server dialog (though the connector should have its own
timeout).

chrome/content/zotero/xpcom/server_connector.js

@@ -538,8 +538,7 @@ Zotero.Server.Connector.SaveSnapshot.prototype = {
 
 						deferred.resolve(201);
 					} catch(e) {
-						Zotero.debug("ERROR");
-						Zotero.debug(e);
+						Zotero.debug(e, 1);
 						deferred.resolve(500);
 						throw e;
 					}

chrome/content/zotero/xpcom/utilities_internal.js

@@ -30,6 +30,8 @@
  * @class Utility functions not made available to translators
  */
 Zotero.Utilities.Internal = {
+	SNAPSHOT_SAVE_TIMEOUT: 15000,
+
 	/**
 	 * Run a function on chunks of a given size of an array's elements.
 	 *
@@ -427,6 +429,7 @@ Zotero.Utilities.Internal = {
 			| nsIWBP.PERSIST_FLAGS_FORCE_ALLOW_COOKIES
 			| nsIWBP.PERSIST_FLAGS_AUTODETECT_APPLY_CONVERSION
 			| nsIWBP.PERSIST_FLAGS_FROM_CACHE
+			| nsIWBP.PERSIST_FLAGS_CLEANUP_ON_FAILURE
 			// Mostly ads
 			| nsIWBP.PERSIST_FLAGS_IGNORE_IFRAMES
 			| nsIWBP.PERSIST_FLAGS_IGNORE_REDIRECTED_DATA;
@@ -447,9 +450,10 @@ Zotero.Utilities.Internal = {
 		const wrapColumn = 80;
 
 		var deferred = Zotero.Promise.defer();
-		wbp.progressListener = new Zotero.WebProgressFinishListener(function () {
+		var listener = new Zotero.WebProgressFinishListener(function () {
 			deferred.resolve();
 		});
+		wbp.progressListener = listener;
 
 		wbp.saveDocument(
 			document,
@@ -460,6 +464,18 @@ Zotero.Utilities.Internal = {
 			wrapColumn
 		);
 
+		// Cancel save after timeout has passed, so we return an error to the connector and don't stay
+		// saving forever
+		var timeoutID = setTimeout(function () {
+			if (deferred.promise.isPending()) {
+				Zotero.debug("Stopping save for " + document.location.href, 2);
+				//Zotero.debug(listener.getRequest());
+				deferred.reject("Snapshot save timeout");
+				wbp.cancelSave();
+			}
+		}, this.SNAPSHOT_SAVE_TIMEOUT);
+		deferred.promise.then(() => clearTimeout(timeoutID));
+
 		return deferred.promise;
 	},
 

chrome/content/zotero/xpcom/zotero.js

@@ -2488,12 +2488,22 @@ Zotero.Browser = new function() {
  * Implements nsIWebProgressListener
  */
 Zotero.WebProgressFinishListener = function(onFinish) {
+	var _request;
+
+	this.getRequest = function () {
+		return _request;
+	};
+
 	this.onStateChange = function(wp, req, stateFlags, status) {
 		//Zotero.debug('onStageChange: ' + stateFlags);
 		if (stateFlags & Components.interfaces.nsIWebProgressListener.STATE_STOP
 				&& stateFlags & Components.interfaces.nsIWebProgressListener.STATE_IS_NETWORK) {
+			_request = null;
 			onFinish();
 		}
+		else {
+			_request = req;
+		}
 	}
 
 	this.onProgressChange = function(wp, req, curSelfProgress, maxSelfProgress, curTotalProgress, maxTotalProgress) {