Fixing a few crashes in the me2me native messaging host.

Fixing a few crashes in the me2me native messaging host.

1. Don't close the delegate read/write handles twice in the me2me native messaging host. The handles are already closed by the native messaging channel in DuplicateHandle.
2. Keep the host alive and send a false response to the client if the user rejects the UAC request.
3. Added some comments.

BUG=325567
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=251529

[weitao, 2014-02-13 23:49:20]

Simple bug fix. PTAL.

[weitao, 2014-02-14 00:48:00]

On 2014/02/13 23:49:20, weitaosu wrote:
> Simple bug fix. PTAL.

Actually please hold off reviewing it. I need to redo this fix with some
changes.

[weitao, 2014-02-14 18:57:17]

The CL now contains two bug fixes in DelegateToElevatedHost. Both are pretty
scoped so it shouldn't be too hard to review them together. :)

[Sergey Ulanov, 2014-02-14 19:26:00]

LGTM.
Please add a short title in the description before the details. I.e. normally CL
message should look as follows:
------
short, one line title 

details
more details

BUG=123123
--

[weitao, 2014-02-14 22:05:56]

The CQ bit was checked by weitaosu@chromium.org

[commit-bot: I haz the power, 2014-02-14 22:09:56]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/weitaosu@chromium.org/165363002/40001

[commit-bot: I haz the power, 2014-02-14 22:43:49]

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

[commit-bot: I haz the power, 2014-02-14 22:43:49]

Retried try job too often on mac_rel for step(s) base_unittests, browser_tests,
interactive_ui_tests, net_unittests, unit_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=mac_rel&nu...

[weitao, 2014-02-15 01:10:23]

The CQ bit was checked by weitaosu@chromium.org

[commit-bot: I haz the power, 2014-02-15 01:12:58]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/weitaosu@chromium.org/165363002/350001

[commit-bot: I haz the power, 2014-02-15 05:08:05]

Change committed as 251529