Add support for python pageset

tools/telemetry/telemetry/page/page_runner.py

Index: tools/telemetry/telemetry/page/page_runner.py
diff --git a/tools/telemetry/telemetry/page/page_runner.py b/tools/telemetry/telemetry/page/page_runner.py
index c57703c3049a2fde652ccc5231f3a3fbeabe2ff9..0e7079a08fce7cf75bb928cbb10a653849eb2c54 100644
--- a/tools/telemetry/telemetry/page/page_runner.py
+++ b/tools/telemetry/telemetry/page/page_runner.py
@@ -268,7 +268,16 @@ def _PrepareAndRunPage(test, page_set, expectations, finder_options,
 
 
 def Run(test, page_set, expectations, finder_options):
-  """Runs a given test against a given page_set with the given options."""
+  if page_set.is_python_pageset:
+    return RunPythonBasedPageSet(test, page_set, expectations, finder_options)
+  else:
+    return RunDictBasedPageSet(test, page_set, expectations, finder_options)
+
+def RunDictBasedPageSet(test, page_set, expectations, finder_options):
+  """Runs a given test against a given page_set with the given options.A
+
+     page_set is an instance of telemetry.page.page_set
+  """
   results = results_options.PrepareResults(test, finder_options)
   browser_options = finder_options.browser_options
 
@@ -486,6 +495,9 @@ def _RunPage(test, page, state, expectation, results, finder_options):
   finally:
     page_state.CleanUpPage()
 
+def RunPythonBasedPageSet(test, page_set, expectations, finder_options):
+  #TODO(nednguyen): implement this
+  pass
 
 def _GetSequentialFileName(base_name):
   """Returns the next sequential file name based on |base_name| and the