Fix the System Profile to not load extensions. It could otherwise be forced to by GPO.

Fix the System Profile to not load extensions. It could otherwise be forced to by GPO.

A few releases ago I introduced a System Profile to back the User Manager (https://codereview.chromium.org/847733005). This profile, however, is causing some problems. I'm trying to reduce those by making clearer the contract of what it's for: A profile that doesn't take a browser window, has no extensions, writes little to disk, etc.

This certainly addresses issue #4 raised within the bug, and address the other issues as well (I can't repro them). This CL generally hardens Chrome for the System Profile in a lot of the same ways we do the Guest Profile.

BUG=482176
TBR=msw@chromium.org

Review URL: https://codereview.chromium.org/1129293002

Cr-Commit-Position: refs/heads/master@{#331276}
(cherry picked from commit 7831f57d5f56e9cafe77388b20a83a90d6eb7918)

Committed: https://chromium.googlesource.com/chromium/src/+/a515307f37fd3c6b7d20a2f93e4654b4f76ab991

[Mike Lerman, 2015-05-27 18:56:53]

Committed patchset #1 (id:1) manually as
a515307f37fd3c6b7d20a2f93e4654b4f76ab991 (presubmit successful).