Fix performance trybots.

tools/run-bisect-perf-regression.py

 #!/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.
 
 """Run Performance Test Bisect Tool
 
 This script is used by a trybot to run the src/tools/bisect-perf-regression.py
 script with the parameters specified in run-bisect-perf-regression.cfg. It will
 check out a copy of the depot in a subdirectory 'bisect' of the working
@@ skipping 252 matching lines @@
 
   results_with_patch = b.RunPerformanceTestAndParseResults(
       opts.command, opts.metric, reset_on_first_run=True, results_label='Patch')
 
   if results_with_patch[1]:
     raise RuntimeError('Patched version failed to run performance test.')
 
   bisect_utils.OutputAnnotationStepClosed()
 
   bisect_utils.OutputAnnotationStepStart('Reverting Patch')
-  if bisect_utils.RunGClient(['revert']):
-    raise RuntimeError('Failed to run gclient runhooks')
+  # TODO: When this is re-written to recipes, this should use bot_update's
+  # revert mechanism to fully revert the client. But for now, since we know that
+  # the perf trybot currently only supports src/ and src/third_party/WebKit, we
+  # simply reset those two directories.
+  bisect_utils.CheckRunGit(['reset', '--hard'])
+  bisect_utils.CheckRunGit(['reset', '--hard'],
+                           os.path.join('third_party', 'WebKit'))
   bisect_utils.OutputAnnotationStepClosed()
 
   bisect_utils.OutputAnnotationStepStart('Building Without Patch')
 
   if bisect_utils.RunGClient(['runhooks']):
     raise RuntimeError('Failed to run gclient runhooks')
 
   if not b.BuildCurrentRevision('chromium'):
     raise RuntimeError('Unpatched version failed to build.')
 
@@ skipping 266 matching lines @@
           config, current_dir, opts.path_to_goma)
 
   print ('Error: Could not load config file. Double check your changes to '
          'run-bisect-perf-regression.cfg or run-perf-test.cfg for syntax '
          'errors.\n')
   return 1
 
 
 if __name__ == '__main__':
   sys.exit(main())