Add everything from src/tools/isolate r159537.

shard_test_cases.py

Index: shard_test_cases.py
diff --git a/shard_test_cases.py b/shard_test_cases.py
new file mode 100755
index 0000000000000000000000000000000000000000..dc8b7828cb0d3184228e47ca62d3dcb6ed902239
--- /dev/null
+++ b/shard_test_cases.py
@@ -0,0 +1,49 @@
+#!/usr/bin/env python
+# Copyright (c) 2012 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.
+
+"""Runs a google-test shard.
+
+This makes a simple interface to run a shard on the command line independent of
+the interpreter, e.g. cmd.exe vs bash.
+"""
+
+import optparse
+import os
+import subprocess
+import sys
+
+
+def fix_python_path(cmd):
+  """Returns the fixed command line to call the right python executable."""
+  out = cmd[:]
+  if out[0] == 'python':
+    out[0] = sys.executable
+  elif out[0].endswith('.py'):
+    out.insert(0, sys.executable)
+  return out
+
+
+def main():
+  parser = optparse.OptionParser(usage='%prog <options> [gtest]')
+  parser.disable_interspersed_args()
+  parser.add_option(
+      '-I', '--index',
+      type='int',
+      default=os.environ.get('GTEST_SHARD_INDEX'),
+      help='Shard index to run')
+  parser.add_option(
+      '-S', '--shards',
+      type='int',
+      default=os.environ.get('GTEST_TOTAL_SHARDS'),
+      help='Total number of shards to calculate from the --index to run')
+  options, args = parser.parse_args()
+  env = os.environ.copy()
+  env['GTEST_TOTAL_SHARDS'] = str(options.shards)
+  env['GTEST_SHARD_INDEX'] = str(options.index)
+  return subprocess.call(fix_python_path(args), env=env)
+
+
+if __name__ == '__main__':
+  sys.exit(main())