Simulate process launch for in-process utility thread

Simulate process launch for in-process utility thread

This ensures that OnProcessLaunched is called on a
UtilityProcessHostImpl even when an in-process utility
thread is in use. The point is to allow Mojo IPC to
utility code even in single-process mode.

BUG=None

Committed: https://crrev.com/eb6ee29760e931d407422e157305effcb4bfbebc
Cr-Commit-Position: refs/heads/master@{#330399}

[Ken Rockot(use gerrit already), 2015-05-16 03:40:10]

rockot@chromium.org changed reviewers:
+ jam@chromium.org

[Ken Rockot(use gerrit already), 2015-05-16 03:40:11]

last one for now, promise

[jam, 2015-05-18 15:47:11]

lgtm

[Ken Rockot(use gerrit already), 2015-05-18 17:35:07]

The CQ bit was checked by rockot@chromium.org

[commit-bot: I haz the power, 2015-05-18 17:35:40]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1138823003/1

[commit-bot: I haz the power, 2015-05-18 20:29:49]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-18 22:42:03]

Patchset 1 (id:??) landed as
https://crrev.com/eb6ee29760e931d407422e157305effcb4bfbebc
Cr-Commit-Position: refs/heads/master@{#330399}