Add integration browser tests for settings hardening.
This CL introduces the PrefHashBrowserTestBase fixture which these tests are based on.
This fixture (in conjunction with the new PREF_HASH_BROWSER_TEST macro) provides an easy way to override 3 methods in order to:
1) Setup Chrome as desired in a PRE_ test.
2) Attack Preferences while Chrome isn't running.
3) Relaunch Chrome and verify reaction to attacks.
The fixture+macro also parametrizes every test such that they are ran in every SettingsEnforcement trial group.
A few pieces were resurrected from the old PrefHashBrowserTest used to test unloaded profile seeding prior to http://crrev.com/277209
Review URL: https://codereview.chromium.org/
431973002
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@287689 0039d316-1c4b-4281-b951-d872f2087c98