Fix issues with token refresh in AccountReconcilor

The CL was change a bit as suggested by the reviewers.

This CL now introduces a worklist model in GoogleAutoLoginHelper. Instead of firing all the refresh token events in a row, it queues up all the login requests and insert GAIA cookies one-by-one. This would let accounts to be appended instead of overwriting one another.

This also introduces GoogleAutoLoginHelperTest for some unit testing.

BUG=305249

Review URL: https://codereview.chromium.org/63253003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238547 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238547