fx-compat: Load zotero://report/ channels as chrome

It seems that the issue wasn't that zotero:// URLs can't be loaded in a content
browser, but rather that the report extension was returning a channel that the
content browser couldn't access. For some reason, it handled that failure by
passing the URL off to the OS, which then opened a duplicate instance of Zotero.

Also:

- Remove ensureBrowserType() and always use <browser type="content"> in
  basicViewer (see b8966f)
- Fix system principal being used to load extensions without `loadAsChrome` set
  to true if an extension with `loadAsChrome` set to true had been loaded in the
  past

chrome/content/zotero/standalone/basicViewer.js

@@ -31,7 +31,10 @@ var browser;
 
 window.addEventListener("load", /*async */function () {
 	browser = document.querySelector('browser');
-	ensureBrowserType('content');
+	
+	browser.addEventListener('pagetitlechanged', () => {
+		document.title = browser.contentTitle || browser.currentURI.spec;
+	});
 	
 	/*
 	browser.setAttribute("remote", "true");
@@ -69,41 +72,8 @@ window.addEventListener("click", function (event) {
 	}
 });
 
-function ensureBrowserType(type) {
-	let oldBrowser = browser;
-	if (!oldBrowser || oldBrowser.getAttribute('type') != type) {
-		browser = document.createXULElement('browser');
-		let attrs = {
-			type,
-			flex: 1,
-			remote: false,
-			maychangeremoteness: true,
-			disableglobalhistory: true,
-		};
-		for (let [attr, value] of Object.entries(attrs)) {
-			browser.setAttribute(attr, value);
-		}
-		if (oldBrowser) {
-			oldBrowser.replaceWith(browser);
-		}
-		else {
-			document.querySelector('#appcontent').append(browser);
-		}
-		browser.addEventListener('pagetitlechanged', () => {
-			document.title = browser.contentTitle || browser.currentURI.spec;
-		});
-		return browser;
-	}
-	else {
-		return oldBrowser;
-	}
-}
-
 function loadURI(uri) {
-	// The zotero protocol handler will not load in a type="content" browser
+	browser.loadURI(
-	// As a temporary fix, replace the browser with one of the correct type if necessary
-	// (The type attribute can't be changed after the browser is created)
-	ensureBrowserType(uri.startsWith('zotero:') ? 'chrome' : 'content').loadURI(
 		uri,
 		{
 			triggeringPrincipal: Services.scriptSecurityManager.getSystemPrincipal(),

components/zotero-protocol-handler.js

@@ -156,7 +156,7 @@ function ZoteroProtocolHandler() {
 	 * Report generation extension for Zotero protocol
 	 */
 	var ReportExtension = {
-		loadAsChrome: false,
+		loadAsChrome: true,
 		
 		newChannel: function (uri, loadInfo) {
 			return new AsyncChannel(uri, loadInfo, function* () {
@@ -1293,10 +1293,6 @@ ZoteroProtocolHandler.prototype = {
 				return this._getCancelledChannel();
 			}
 			
-			if (!this._principal && ext.loadAsChrome) {
-				this._principal = Services.scriptSecurityManager.getSystemPrincipal();
-			}
-			
 			var extChannel = ext.newChannel(uri, loadInfo);
 			// Extension returned null, so cancel request
 			if (!extChannel) {
@@ -1304,7 +1300,10 @@ ZoteroProtocolHandler.prototype = {
 			}
 			
 			// Apply cached principal to extension channel
-			if (this._principal) {
+			if (ext.loadAsChrome) {
+				if (!this._principal) {
+					this._principal = Services.scriptSecurityManager.getSystemPrincipal();
+				}
 				extChannel.owner = this._principal;
 			}