Move experiment logic out of PasswordManager and into PasswordManagerDelegate.

As part of componentizing the password manager, we need to remove all
references to chrome/.

BUG=335119
R=gcasto@chromium.org

Review URL: https://codereview.chromium.org/151913009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249444 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249444