This is the fifth CL of several that will eventually replace TokenService with
ProfileOAuth2TokenService. In this CL, the following changes are made:

1/ inline sign in is switched to PO2TS
2/ SigninManager dependencies are fixed up
3/ minor comment cleanup and removing header files.

BUG=305247

Review URL: https://codereview.chromium.org/24494002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237222 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 237222