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=jcivelli@chromium.org (a function, called from chrome/test that lives in c/b/profiles, was renamed).
Review URL: https://codereview.chromium.org/
1129293002
Cr-Commit-Position: refs/heads/master@{#331276}