Introduce a new tool to diagnose setup.exe's stage timings without having to instrument setup.exe itself.

Here is an example output when observing an update from M29 to M30 via a diff-installer on an XP VM:
"""
No ongoing stage, waiting for next install/update cycle...
12/10/13 17:22:55: Starting stage 2...
12/10/13 17:23:06: Stage 2 took 10.03 seconds.
12/10/13 17:23:06: Starting stage 4...
12/10/13 17:23:52: Stage 4 took 46.32 seconds.
12/10/13 17:23:52: Starting stage 17...
12/10/13 17:23:52: Stage 17 took 0.04 seconds.
12/10/13 17:23:52: Starting stage 6...
12/10/13 17:23:52: Stage 6 took 0.06 seconds.
12/10/13 17:23:52: Starting stage 7...
12/10/13 17:23:52: Stage 7 took 0.50 seconds.
12/10/13 17:23:52: Starting stage 9...
12/10/13 17:23:54: Stage 9 took 1.28 seconds.
12/10/13 17:23:54: Starting stage 12...
12/10/13 17:23:54: Stage 12 took 0.56 seconds.
12/10/13 17:23:54: Starting stage 15...
12/10/13 17:23:55: Stage 15 took 0.20 seconds.
12/10/13 17:23:55: Install/update complete, stages timings:
[
  {
    "stage": 2,
    "time": 10.029999999999999
  },
  {
    "stage": 4,
    "time": 46.32
  },
  {
    "stage": 17,
    "time": 0.040000000000000001
  },
  {
    "stage": 6,
    "time": 0.059999999999999998
  },
  {
    "stage": 7,
    "time": 0.5
  },
  {
    "stage": 9,
    "time": 1.28
  },
  {
    "stage": 12,
    "time": 0.56000000000000005
  },
  {
    "stage": 15,
    "time": 0.20000000000000001
  }
]
12/10/13 17:23:55: No more stages, waiting for next install/update cycle...
"""

NOTRY=True
BUG=167622

Review URL: https://codereview.chromium.org/109003003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241020 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241020