MultiProcessTest: Update SpawnChild* to return a Process.

MultiProcessTest: Update SpawnChild* to return a Process.

We should not be dealing with raw handles.

BUG=417532
Committed: https://crrev.com/07b589c1f6c4d0aac24e270a13fa83031bf2038c
Cr-Commit-Position: refs/heads/master@{#311127}

[rvargas (doing something else), 2015-01-10 01:10:03]

rvargas@chromium.org changed reviewers:
+ avi@chromium.org, siggi@chromium.org

[rvargas (doing something else), 2015-01-10 01:10:03]

PTAL:
avi -> content

[rvargas (doing something else), 2015-01-10 01:19:35]

rvargas@chromium.org changed reviewers:
+ agl@chromium.org, jamesr@chromium.org, morrita@chromium.org,
rsesek@chromium.org, thakis@chromium.org, thestig@chromium.org

[rvargas (doing something else), 2015-01-10 01:19:36]

PTAL:

thestig -> base
thakis -> chrome
siggi -> components
avi -> content
agl -> ipc
morrita -> ipc/mojo/ipc_channel_mojo_unittest.cc
jamesr -> mojo
rsesek -> sandbox

[agl, 2015-01-10 01:33:12]

ipc LGTM.

[Lei Zhang, 2015-01-10 01:57:19]

base/ lgtm

[Nico, 2015-01-10 02:43:27]

chrome lgtm

[Hajime Morrita, 2015-01-10 02:53:44]

ipc/mojo lgtm.

[Avi (use Gerrit), 2015-01-10 05:11:34]

lgtm

Yay for OOP! 🍻

[Sigurður Ásgeirsson, 2015-01-10 19:49:56]

components lgtm

[Robert Sesek, 2015-01-12 17:24:20]

sandbox/ LGTM

[jamesr, 2015-01-12 21:10:42]

lgtm

[rvargas (doing something else), 2015-01-12 22:17:27]

The CQ bit was checked by rvargas@chromium.org

[commit-bot: I haz the power, 2015-01-12 22:18:36]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/843113003/1

[commit-bot: I haz the power, 2015-01-12 22:23:51]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-01-12 22:25:38]

Patchset 1 (id:??) landed as
https://crrev.com/07b589c1f6c4d0aac24e270a13fa83031bf2038c
Cr-Commit-Position: refs/heads/master@{#311127}