[telemetry] Prototype for specifying page sets using Python imports and Telemetry discovery.

tools/perf/run_benchmark

 #!/usr/bin/env python
 # Copyright (c) 2013 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 os
 import sys
 
 sys.path.append(os.path.join(os.path.dirname(__file__), os.pardir, 'telemetry'))
 
 from telemetry import test_runner
-from telemetry.core import environment
 
 
 if __name__ == '__main__':
-  base_dir = os.path.dirname(os.path.realpath(__file__))
+  top_level_dir = os.path.dirname(os.path.realpath(__file__))
   test_aliases = {
       'blink_perf': 'blink_perf.all',
       'image_decoding.tough_decoding_cases':
           'image_decoding.image_decoding_measurement',
       'media.tough_media_cases': 'media.tough_video_cases',
       'page_cycler.pica': 'pica.pica',
   }
-  test_runner.config = environment.Environment([base_dir], test_aliases)
-  sys.exit(test_runner.main())
+
+  environment = test_runner.Environment(
+    top_level_dir=top_level_dir,
+    test_dirs=[os.path.join(top_level_dir, 'benchmarks')],
+    page_test_dirs=[os.path.join(top_level_dir, 'measurements')],
+    page_set_dirs=[os.path.join(top_level_dir, 'page_sets')],
+    test_aliases=test_aliases
+  )
+  sys.exit(test_runner.main(environment))