[tools/perf] Add integration test for about://tracing UI

tools/perf/core/about_tracing_integration_test.py

+# Copyright 2016 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+from telemetry import decorators
+from telemetry.testing import tab_test_case
+
+
+_RECORD_BUTTON_SELECTOR_FUNC = '''
+}'''

[sullivan, 2016/07/27 12:40:39]

What's this for?

[nednguyen, 2016/07/27 12:56:52]

Removed.

+
+
+class AboutTracingIntegrationTest(tab_test_case.TabTestCase):
+
+  @decorators.Disabled('android')
+  def testBasicTraceRecording(self):
+    action_runner = self._tab.action_runner
+    action_runner.Navigate('chrome://tracing')
+
+    # Click 'record' to trigger record selection diaglog.
+    action_runner.WaitForElement(element_function='''function() {
+        return document.querySelector('tr-ui-timeline-view').shadowRoot.

[sullivan, 2016/07/27 12:40:39]

I wanted to check that you tested this at ToT? The migration guide warns against
using shadowRoot in 1.0 (buried here:
https://www.polymer-project.org/1.0/docs/migration#dom-apis) but I don't see
clear guidance on how well it is supported.

+Kari I've seen you make changes from shadowRoot -> root did you find clear docs
on this anywhere?

(If the tests pass we can discuss this for a follow up)

[nednguyen, 2016/07/27 12:56:52]

Done.

+                   getElementById('record-button');}''')
+    action_runner.ExecuteJavaScript('''
+        document.querySelector('tr-ui-timeline-view').shadowRoot.
+            getElementById('record-button').click();''')

[sullivan, 2016/07/27 12:40:39]

Why not use the ClickElement method in action_runner here and below?

[nednguyen, 2016/07/27 12:56:52]

Done.

+
+    # Wait for record selection diaglog to pop up, then click record.
+    action_runner.WaitForElement(selector='.overlay')
+    action_runner.ExecuteJavaScript('''
+        document.querySelector('.overlay').shadowRoot.
+             querySelectorAll('button')[0].click()''')
+
+    # Stop recording after 1 seconds.
+    action_runner.Wait(1)
+    action_runner.ExecuteJavaScript('''
+        document.querySelector('.overlay').
+            querySelectorAll('button')[0].click()''')
+
+    # Make sure that we can see the browser track.
+    action_runner.WaitForElement(selector='div[title~="Browser"]')