Update docs and command line flags for MB.

Update docs and command line flags for MB.

This adds the information about how the integration w/ isolates works,
and does a bunch of additional cleanup to make sure everything is
documented and in sync.

R=maruel@chromium.org
BUG=

Committed: https://crrev.com/747cb269970294b7928ca30a3cde192c90072d13
Cr-Commit-Position: refs/heads/master@{#338951}

[M-A Ruel, 2015-06-25 13:31:13]

lgtm, thanks

https://codereview.chromium.org/1206633003/diff/20001/tools/mb/mb.py
File tools/mb/mb.py (right):

https://codereview.chromium.org/1206633003/diff/20001/tools/mb/mb.py#newcode68
tools/mb/mb.py:68: help=('Do not print anything on success, '
Why add () ?

[Dirk Pranke, 2015-06-25 16:06:15]

https://codereview.chromium.org/1206633003/diff/20001/tools/mb/mb.py
File tools/mb/mb.py (right):

https://codereview.chromium.org/1206633003/diff/20001/tools/mb/mb.py#newcode68
tools/mb/mb.py:68: help=('Do not print anything on success, '
On 2015/06/25 13:31:13, M-A Ruel wrote:
> Why add () ?

Habit, I think :). Will remove.

[Dirk Pranke, 2015-07-15 20:42:53]

The CQ bit was checked by dpranke@chromium.org

[Dirk Pranke, 2015-07-15 20:42:53]

The patchset sent to the CQ was uploaded after l-g-t-m from maruel@chromium.org
Link to the patchset: https://codereview.chromium.org/1206633003/#ps40001
(title: "merge to HEAD and update w/ review feedback")

[commit-bot: I haz the power, 2015-07-15 20:45:05]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1206633003/40001

[commit-bot: I haz the power, 2015-07-15 20:58:42]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-07-15 20:58:42]

Try jobs failed on following builders:
  linux_chromium_chromeos_compile_dbg_ng on tryserver.chromium.linux
(JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

(exceeded global retry quota)

[Dirk Pranke, 2015-07-15 21:02:30]

The CQ bit was checked by dpranke@chromium.org

[commit-bot: I haz the power, 2015-07-15 21:03:04]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1206633003/40001

[commit-bot: I haz the power, 2015-07-15 21:12:33]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-07-15 21:12:33]

Try jobs failed on following builders:
  android_clang_dbg_recipe on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/android_clang_d...)

(exceeded global retry quota)

[Dirk Pranke, 2015-07-15 22:55:46]

The CQ bit was checked by dpranke@chromium.org

[commit-bot: I haz the power, 2015-07-15 22:56:34]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1206633003/40001

[commit-bot: I haz the power, 2015-07-15 23:53:35]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-07-15 23:54:38]

Patchset 3 (id:??) landed as
https://crrev.com/747cb269970294b7928ca30a3cde192c90072d13
Cr-Commit-Position: refs/heads/master@{#338951}

[tsergeant, 2015-07-16 01:32:40]

A revert of this CL (patchset #3 id:40001) has been created in
https://codereview.chromium.org/1234343003/ by tsergeant@chromium.org.

The reason for reverting is: This CL appears to be causing tryjobs to fail. See:

http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...

and https://crbug.com/510655.