SandboxIPCProcess: make shutdown mechanism explicit.

SandboxIPCProcess: make shutdown mechanism explicit.

In order to move SandboxIPCProcess into a thread, we need a mechanism
to make that thread exit.

BUG=322185
TEST=content_shell loads webpages, browser shuts down correctly.

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=272350

[Jorge Lucangeli Obes, 2014-05-21 23:51:14]

This supersedes https://chromiumcodereview.appspot.com/270983002/, using
|lifeline_fd| explicitly to signal SandboxIPCProcess to exit.

Removing '_exit(0)' from SandboxIPCProcess::Run() is not a problem because the
function calling ::Run() does _exit(0) immediately after ::Run(), and this
_exit(0) call in ::Run() would have been removed by the follow-up CL making this
a thread.

Thanks!

[piman, 2014-05-22 00:13:30]

lgtm

[Jorge Lucangeli Obes, 2014-05-22 18:11:26]

+Matthew. Do you mind taking a look instead of Julien? He's probably swamped.

[mdempsky, 2014-05-22 18:13:44]

lgtm

[Jorge Lucangeli Obes, 2014-05-22 18:14:15]

The CQ bit was checked by jorgelo@chromium.org

[commit-bot: I haz the power, 2014-05-22 18:18:57]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/jorgelo@chromium.org/291173009/1

[commit-bot: I haz the power, 2014-05-22 22:42:04]

Change committed as 272350