Handle ListAccount fetches and watching the GAIA cookies from within the GaiaCookieManagerService.
This CL only implements non-ChromeOS features; AboutSigninInterals and the AccountReconcilor. ChromeOS features will come later, as they require more support. This CL also removes the ReconcilorSource as a parameter to ListAccounts. Changes the observed cookie from the LSID cookie to the APISID cookie at nickk@'s suggestion.
Design doc: https://docs.google.com/document/d/1FfmSS7M87L_2tkVuHO3NuruborFm6qHXe2VdktZg-HQ/
BUG=466799, 463611, 471210
Review URL: https://codereview.chromium.org/
1075273002
Cr-Commit-Position: refs/heads/master@{#326846}