Bug 1661138 - Make WPT print reftests not open new windows. r=jgraham,marionette-reviewers

As it's too slow (specially on Android and WebRender) and causes tests
to timeout semi-randomly.

In order to do that, implement nsIBrowserDOMWindow in the reftest
window, in a way that keeps the existing behavior for all other things
we care about.

While at it, remove the renderroot attribute which is just leftover (no
longer exists).

Differential Revision: https://phabricator.services.mozilla.com/D91186

layout/tools/reftest/reftest.xhtml

@@ -7,9 +7,7 @@
         hidechrome="true"
         onload="OnRefTestLoad();"
         onunload="OnRefTestUnload();"
-        style="background:white; overflow:hidden"
-        renderroot="content"
-        >
+        style="background:white; overflow:hidden">
     <script type="application/ecmascript" src="resource://reftest/reftest.jsm" />
     <!-- The reftest browser element is dynamically created, here -->
 </window>

testing/marionette/jar.mn

@@ -37,6 +37,7 @@ marionette.jar:
   content/proxy.js (proxy.js)
   content/reftest.js (reftest.js)
   content/reftest.xhtml (reftest.xhtml)
+  content/reftest-content.js (reftest-content.js)
   content/server.js (server.js)
   content/stream-utils.js (stream-utils.js)
   content/sync.js (sync.js)

testing/marionette/reftest-content.js

@@ -0,0 +1,72 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { XPCOMUtils } = ChromeUtils.import(
+  "resource://gre/modules/XPCOMUtils.jsm"
+);
+
+XPCOMUtils.defineLazyScriptGetter(
+  this,
+  "PrintUtils",
+  "chrome://global/content/printUtils.js"
+);
+
+// This is an implementation of nsIBrowserDOMWindow that handles only opening
+// print browsers, because the "open a new window fallback" is just too slow
+// in some cases and causes timeouts.
+function BrowserDOMWindow() {}
+BrowserDOMWindow.prototype = {
+  QueryInterface: ChromeUtils.generateQI(["nsIBrowserDOMWindow"]),
+
+  _maybeOpen(aOpenWindowInfo, aWhere) {
+    if (aWhere == Ci.nsIBrowserDOMWindow.OPEN_PRINT_BROWSER) {
+      return PrintUtils.startPrintWindow(
+        aOpenWindowInfo.parent,
+        aOpenWindowInfo
+      );
+    }
+    return null;
+  },
+
+  createContentWindow(
+    aURI,
+    aOpenWindowInfo,
+    aWhere,
+    aFlags,
+    aTriggeringPrincipal,
+    aCsp
+  ) {
+    return this._maybeOpen(aOpenWindowInfo, aWhere)?.browsingContext;
+  },
+
+  openURI(aURI, aOpenWindowInfo, aWhere, aFlags, aTriggeringPrincipal, aCsp) {
+    return this._maybeOpen(aOpenWindowInfo, aWhere)?.browsingContext;
+  },
+
+  createContentWindowInFrame(aURI, aParams, aWhere, aFlags, aName) {
+    return this._maybeOpen(aParams.openWindowInfo, aWhere);
+  },
+
+  openURIInFrame(aURI, aParams, aWhere, aFlags, aName) {
+    return this._maybeOpen(aParams.openWindowInfo, aWhere);
+  },
+
+  canClose() {
+    return true;
+  },
+
+  get tabCount() {
+    return 1;
+  },
+
+  isTabContentWindow(win) {
+    // This method is probably not needed anymore: bug 1602915
+    // In any case this gives us the default behavior.
+    return false;
+  },
+};
+
+window.browserDOMWindow = new BrowserDOMWindow();

testing/marionette/reftest.xhtml

@@ -1,6 +1,6 @@
 <window id="reftest"
         xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
         hidechrome="true"
-        style="background-color:white; overflow:hidden"
-        renderroot="content">
-</window>
+        style="background-color:white; overflow:hidden">
+  <script src="reftest-content.js"></script>
+</window>