[Chrome OS] Respect periods in google apps account names

When logging in to @gmail.com accounts via the web, . characters are
ignored -- which we do on chrome OS.  When logging into google apps
accounts for OTHER domains, . characters should NOT be ignored.  We
were canonicalizing them out on Chrome OS, breaking login for apps
users who have . embedded in their usernames.

BUG=chromium-os:10397
TEST=unit tests, install on device and try cmasone@gmail.com, c.masone@gmail.com, why.you@mydomain.org and whyyou@mydomain.org.  The first three work, the last one does not, as expected.

Review URL: http://codereview.chromium.org/6089004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@70318 0039d316-1c4b-4281-b951-d872f2087c98