Componentize PasswordManager and PasswordFormManager unittests.

The changes involved are straightforward.

BUG=348522,348517
R=vabr@chromium.org

Review URL: https://codereview.chromium.org/190453002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255576 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255576