Disable tracing in user service

Disable tracing in user service

Two problems:

 1. The tracing client library makes some now-invalid
    assumptions about its environment
 2. We don't have a tracing shell client setup properly
    for chrome or browser tests.

The second problem in particular is causing bad behavior
on OS X if anyone tries connecting to mojo:tracing.

This CL removes tracing usage from UserShellClient for
now.

BUG=609632
R=erg@chromium.org

Committed: https://crrev.com/ad48a137fd13bf0966c58f17b667f3828dcd89ed
Cr-Commit-Position: refs/heads/master@{#392378}

[Elliot Glaysher, 2016-05-09 17:44:37]

lgtm

[Ken Rockot(use gerrit already), 2016-05-09 17:45:10]

The CQ bit was checked by rockot@chromium.org

[commit-bot: I haz the power, 2016-05-09 17:45:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1963753002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1963753002/1

[commit-bot: I haz the power, 2016-05-09 18:36:14]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-05-09 18:37:58]

Description was changed from

==========
Disable tracing in user service

Two problems:

 1. The tracing client library makes some now-invalid
    assumptions about its environment
 2. We don't have a tracing shell client setup properly
    for chrome or browser tests.

The second problem in particular is causing bad behavior
on OS X if anyone tries connecting to mojo:tracing.

This CL removes tracing usage from UserShellClient for
now.

BUG=609632
R=erg@chromium.org
==========

to

==========
Disable tracing in user service

Two problems:

 1. The tracing client library makes some now-invalid
    assumptions about its environment
 2. We don't have a tracing shell client setup properly
    for chrome or browser tests.

The second problem in particular is causing bad behavior
on OS X if anyone tries connecting to mojo:tracing.

This CL removes tracing usage from UserShellClient for
now.

BUG=609632
R=erg@chromium.org

Committed: https://crrev.com/ad48a137fd13bf0966c58f17b667f3828dcd89ed
Cr-Commit-Position: refs/heads/master@{#392378}
==========

[commit-bot: I haz the power, 2016-05-09 18:38:00]

Patchset 1 (id:??) landed as
https://crrev.com/ad48a137fd13bf0966c58f17b667f3828dcd89ed
Cr-Commit-Position: refs/heads/master@{#392378}