[Telemetry] Add action_runner property to Tab

telemetry/telemetry/internal/browser/tab.py

Index: telemetry/telemetry/internal/browser/tab.py
diff --git a/telemetry/telemetry/internal/browser/tab.py b/telemetry/telemetry/internal/browser/tab.py
index 9c1f79f9e16471b44df3ff6fc4036d0fd04435c2..54bcf19379cfc76404218a608060e99eea7207ce 100644
--- a/telemetry/telemetry/internal/browser/tab.py
+++ b/telemetry/telemetry/internal/browser/tab.py
@@ -23,6 +23,7 @@ class Tab(web_contents.WebContents):
     super(Tab, self).__init__(inspector_backend)
     self._tab_list_backend = tab_list_backend
     self._browser = browser
+    self._action_runner = None
 
   @property
   def browser(self):
@@ -30,6 +31,13 @@ class Tab(web_contents.WebContents):
     return self._browser
 
   @property
+  def action_runner(self):
+    if self._action_runner is None:
+      from telemetry.page import action_runner

[nednguyen, 2016/04/06 14:55:49]

Ah, seems like the bug here is action_runner module lives in page package.

+      self._action_runner = action_runner.ActionRunner(self)
+    return self._action_runner
+
+  @property
   def url(self):
     """Returns the URL of the tab, as reported by devtools.