Add Wait* API to ActionRunner to wrap over WaitAction.

tools/perf/page_sets/indexeddb_offline.py

 # Copyright 2014 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.
+
+import re
+
 # pylint: disable=W0401,W0614
 from telemetry.page.actions.all_page_actions import *
 from telemetry.page import page as page_module
 from telemetry.page import page_set as page_set_module
 
 
+def _CreateXpathFunction(xpath):
+  return ('document.evaluate(%s, document, null, '
+          'XPathResult.FIRST_ORDERED_NODE_TYPE, null)'
+          '.singleNodeEvaluate') % re.escape(xpath)
+
+
 class IndexeddbOfflinePage(page_module.Page):
 
   """ Why: Simulates user input while offline and sync while online. """
 
   def __init__(self, page_set):
     super(IndexeddbOfflinePage, self).__init__(
       url='file://endure/indexeddb_app.html',
       page_set=page_set,
       name='indexeddb_offline')
     self.user_agent_type = 'desktop'
 
   def RunNavigateSteps(self, action_runner):
     action_runner.NavigateToPage(self)
-    action_runner.RunAction(WaitAction(
-        {
-            'text': 'initialized',
-            'condition': 'element'
-        }))
+    action_runner.WaitForElement(text='initialized')
 
   def RunEndure(self, action_runner):
-    action_runner.RunAction(WaitAction(
-        {
-            'condition': 'element',
-            'selector': 'button[id="online"]:not(disabled)'
-        }))
+    action_runner.WaitForElement('button[id="online"]:not(disabled)')
     action_runner.RunAction(ClickElementAction(
         {
             'selector': 'button[id="online"]:not(disabled)'
         }))
-    action_runner.RunAction(WaitAction(
-        {
-            'xpath': 'id("state")[text()="online"]',
-            'condition': 'element'
-        }))
-    action_runner.RunAction(WaitAction(
-        {
-            "seconds": 1
-        }))
-    action_runner.RunAction(WaitAction(
-        {
-            'condition': 'element',
-            'selector': 'button[id="offline"]:not(disabled)'
-        }))
+    action_runner.WaitForElement(
+        element_function=_CreateXpathFunction('id("state")[text()="online"]'))
+    action_runner.Wait(1)
+    action_runner.WaitForElement('button[id="offline"]:not(disabled)')
     action_runner.RunAction(ClickElementAction(
         {
             'selector': 'button[id="offline"]:not(disabled)'
         }))
-    action_runner.RunAction(WaitAction(
-        {
-            'xpath': 'id("state")[text()="offline"]',
-            'condition': 'element'
-        }))
+    action_runner.WaitForElement(
+        element_function=_CreateXpathFunction('id("state")[text()="offline"]'))
 
 
 class IndexeddbOfflinePageSet(page_set_module.PageSet):
 
   """ Chrome Endure test for IndexedDB. """
 
   def __init__(self):
     super(IndexeddbOfflinePageSet, self).__init__(
         user_agent_type='desktop')
 
     self.AddPage(IndexeddbOfflinePage(self))