OAuth2 sign-in flow for ChromeOS.

Refactored all OAuth1/2 code out of LoginUtils into OAuthLoginManager class.

Created OAuth2-based specialization of OAuthLoginManager (behind --force-oauth2 switch). This new class uses OAuth2 refresh tokens as a base token from which all others are minted - incl. GAIA credentials and session cookies.

BUG=166192,  169999
TEST=existing unit, browser tests, additional manual testing
TBR=sky

Review URL: https://codereview.chromium.org/11649055

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@176800 0039d316-1c4b-4281-b951-d872f2087c98
48 files changed