Add support for python pageset

tools/telemetry/telemetry/page/actions/page_action.py

Index: tools/telemetry/telemetry/page/actions/page_action.py
diff --git a/tools/telemetry/telemetry/page/actions/page_action.py b/tools/telemetry/telemetry/page/actions/page_action.py
index 17b42efcc6a5718b9cf171ca70977fbe2be812e8..b1e68620913794c9bdc07c6c3efedd90a46042c6 100644
--- a/tools/telemetry/telemetry/page/actions/page_action.py
+++ b/tools/telemetry/telemetry/page/actions/page_action.py
@@ -19,11 +19,14 @@ class PageAction(object):
 
   def __init__(self, attributes=None):
     if attributes:
-      for k, v in attributes.iteritems():
-        setattr(self, k, v)
+      self.SetAttributes(attributes)
     self._timeline_marker_base_name = None
     self._timeline_marker_id = None
 
+  def SetAttributes(self, attributes):
+    for k, v in attributes.iteritems():
+      setattr(self, k, v)
+
   def CustomizeBrowserOptionsForPageSet(self, options):
     """Override to add action-specific options to the BrowserOptions
     object. These options will be set for the whole page set.