Reland of Delay Input.dispatchKeyEvent response until after key event ack.

content/public/test/browser_test_utils.cc

Index: content/public/test/browser_test_utils.cc
diff --git a/content/public/test/browser_test_utils.cc b/content/public/test/browser_test_utils.cc
index fac5648880c519b993b51a6d58b811a896783b1c..99839d5565f52566dd14ce091f2147d47b731733 100644
--- a/content/public/test/browser_test_utils.cc
+++ b/content/public/test/browser_test_utils.cc
@@ -1530,9 +1530,13 @@ bool InputMsgWatcher::OnMessageReceived(const IPC::Message& message) {
   return false;
 }
 
+bool InputMsgWatcher::HasReceivedAck() const {
+  return ack_result_ != INPUT_EVENT_ACK_STATE_UNKNOWN;
+}
+
 uint32_t InputMsgWatcher::WaitForAck() {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
-  if (ack_result_ != INPUT_EVENT_ACK_STATE_UNKNOWN)
+  if (HasReceivedAck())
     return ack_result_;
   base::RunLoop run_loop;
   base::AutoReset<base::Closure> reset_quit(&quit_, run_loop.QuitClosure());