Bug 1663429 - [marionette] Only throw NoSuchWindow error in...

Bug 1663429 - [marionette] Only throw NoSuchWindow error in "WebDriver:SwitchToWindow". r=jgraham, a=RyanVM

There is a race condition in the "WebDriver:SwitchToWindow" command
that would throw an UnknownError instead of NoSuchWindowError when
the window gets closed at the same time as the command gets called.

Differential Revision: https://phabricator.services.mozilla.com/D89377

testing/marionette/driver.js

@@ -1630,6 +1630,9 @@ GeckoDriver.prototype.setWindowRect = async function(cmd) {
  * @param {boolean=} focus
  *     A boolean value which determines whether to focus
  *     the window. Defaults to true.
+ *
+ * @throws {NoSuchWindowError}
+ *     Top-level browsing context has been discarded.
  */
 GeckoDriver.prototype.switchToWindow = async function(cmd) {
   const { focus = true, handle } = cmd.parameters;
@@ -1642,9 +1645,18 @@ GeckoDriver.prototype.switchToWindow = async function(cmd) {
 
   const id = parseInt(handle);
   const found = this.findWindow(this.windows, (win, winId) => id == winId);
+
+  let selected = false;
   if (found) {
+    try {
       await this.setWindowHandle(found, focus);
-  } else {
+      selected = true;
+    } catch (e) {
+      logger.error(e);
+    }
+  }
+
+  if (!selected) {
     throw new NoSuchWindowError(`Unable to locate window: ${handle}`);
   }
 };