Implement dtrace log parsing for MacOSX.

tools/isolate/trace_child_process.py

+#!/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.
+
+"""Waits for the go signal and replaces itself with the command to be run.
+
+Not meant to be used directly, only meant to be used by trace_inputs.py.
+"""
+
+import os
+import subprocess
+import sys
+
+
+def main():
+  signal = 'Go!'
+  value = sys.stdin.read(len(signal))
+  assert value == signal
+  sys.stdin.close()
+  # Replace the executable with an absolute path to make it easier to grok.
+  cmd = sys.argv[1:]
+  cmd[0] = os.path.abspath(cmd[0])
+  if cmd[0].endswith('.py'):
+    cmd.insert(0, sys.executable)
+  p = subprocess.Popen(cmd)
+  #print 'Child pid: %d' % p.pid
+  p.wait()
+  return p.returncode
+
+
+if __name__ == '__main__':
+  sys.exit(main())