[perf] Improve InputWithSelector login helper

Add timeout before and after setting the focus. Otherwise it's quite likely
that we drop one or two characters when using InputWithSelector.

Bug: 878390
Change-Id: Ib703447425160eb87683143a61e03461af1795b7
Reviewed-on: https://chromium-review.googlesource.com/c/1256984Reviewed-by: Juan Antonio Navarro Pérez <perezju@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595920}

tools/perf/page_sets/login_helpers/login_utils.py

@@ -54,10 +54,14 @@ def InputWithSelector(action_runner, input_text, input_selector):
       possible exceptions.
   """
   action_runner.WaitForElement(selector=input_selector)
+  action_runner.Wait(0.5)
   # Focus the requested element first and then enter text using single
   # Keyboard events to bypass certain restrictions on websites.
   action_runner.ExecuteJavaScript(
       'document.querySelector({{selector}}).focus()', selector=input_selector)
+  # Wait a bit to make sure the focus is properly set, otherwise we'll end up
+  # losing some characters.
+  action_runner.Wait(0.5)
   action_runner.EnterText(input_text)
 
 def InputForm(action_runner, input_text, input_id, form_id=None):