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

content/test/gpu/run_gpu_test.py

 #!/usr/bin/env python
 # 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 os
 import sys
 
 sys.path.append(os.path.join(os.path.dirname(__file__),
     os.pardir, os.pardir, os.pardir, 'tools', 'telemetry'))
 
 from telemetry import test_runner
-from telemetry.core import environment
 
 
 if __name__ == '__main__':
-  base_dir = os.path.dirname(os.path.realpath(__file__))
-  test_runner.config = environment.Environment([base_dir])
-  sys.exit(test_runner.main())
+  top_level_dir = os.path.dirname(os.path.realpath(__file__))
+  environment = test_runner.Environment(
+    top_level_dir=top_level_dir,
+    test_dirs=[os.path.join(top_level_dir, 'gpu_tests')],
+    page_set_dirs=[os.path.join(top_level_dir, 'page_sets')]
+  )
+  sys.exit(test_runner.main(environment))