[ChromeDriver] Fix JS code syntax error

Fixing a JavaScript code syntax error in the code intended to cause a
two frame wait before dispatching touch events.

Bug: chromedriver:2665
Change-Id: I7a69a58500fdae5fdb45ab836eb96c054f8e54b9
Reviewed-on: https://chromium-review.googlesource.com/c/1340582Reviewed-by: Joel Einbinder <einbinder@chromium.org>
Commit-Queue: John Chen <johnchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609825}

chrome/test/chromedriver/chrome/web_view_impl.cc

@@ -409,7 +409,7 @@ Status WebViewImpl::DispatchTouchEventsForMouseEvents(
   // thread to get consistent behavior.
   base::DictionaryValue params;
   params.SetString("expression",
-                   "new Promise(x => setTimeout(() => setTimeout(x, 20), 20)");
+                   "new Promise(x => setTimeout(() => setTimeout(x, 20), 20))");
   params.SetBoolean("awaitPromise", true);
   client_->SendCommand("Runtime.evaluate", params);
   for (auto it = events.begin(); it != events.end(); ++it) {