Allow RemoteContextHelper to open windows from remote contexts

html/browsers/browsing-the-web/remote-context-helper-tests/addWindow-from-window.window.js

@@ -0,0 +1,16 @@
+// META: title=RemoteContextHelper with defaults
+// META: script=/common/dispatcher/dispatcher.js
+// META: script=/common/get-host-info.sub.js
+// META: script=/common/utils.js
+// META: script=/html/browsers/browsing-the-web/remote-context-helper/resources/remote-context-helper.js
+// META: script=./resources/test-helper.js
+
+'use strict';
+
+promise_test(async t => {
+  const rcHelper = new RemoteContextHelper();
+  const main = await rcHelper.addWindow();
+  const childWindow = await main.addWindow();
+  await assertSimplestScriptRuns(childWindow);
+  await assertOriginIsAsExpected(childWindow, location.origin);
+});

html/browsers/browsing-the-web/remote-context-helper/resources/remote-context-helper.js

@@ -320,19 +320,29 @@
     url.searchParams.append('pipe', formattedHeaders.join('|'));
   }
 
-  function windowExecutorCreator({target = '_blank', features} = {}) {
-    return (url, documentContent) => {
-      if (url && url.substring(0, 5) == 'data:') {
-        throw new TypeError('Windows cannot use data: URLs.');
-      }
-
+  function windowExecutorCreator(
+    { target = '_blank', features } = {}, remoteContextWrapper) {
+    let openWindow = (url, target, features, documentContent) => {
       const w = window.open(url, target, features);
       if (documentContent) {
         w.document.open();
         w.document.write(documentContent);
         w.document.close();
       }
     };
+
+    return (url, documentContent) => {
+      if (url && url.substring(0, 5) == 'data:') {
+        throw new TypeError('Windows cannot use data: URLs.');
+      }
+
+      if (remoteContextWrapper) {
+        return remoteContextWrapper.executeScript(
+          openWindow, [url, target, features, documentContent]);
+      } else {
+        openWindow(url, target, features, documentContent);
+      }
+    };
   }
 
   function elementExecutorCreator(
@@ -527,6 +537,23 @@
       });
     }
 
+    /**
+     * Opens a window from the remote context. @see createContext for
+     * @param {RemoteContextConfig|object} [extraConfig]
+     * @param {Object} [options]
+     * @param {string} [options.target] Passed to `window.open` as the
+     *     2nd argument
+     * @param {string} [options.features] Passed to `window.open` as the
+     *     3rd argument
+     * @returns {Promise<RemoteContextWrapper>} The remote context.
+     */
+    addWindow(extraConfig, options) {
+      return this.helper.createContext({
+        executorCreator: windowExecutorCreator(options, this),
+        extraConfig,
+      });
+    }
+
     /**
      * Adds a dedicated worker to the current document.
      * @param {string|null} [globalVariable] The name of the global variable to