[Chromoting] Add support for getUserInfo.
getUserInfo is similar to getEmail except that it gets the user's name
in addition to email address. Since it requires a separate Google API
permission, there are separate getUserInfo vs. getEmail apis rather than
always getting (and requiring permission for) both.
The new getUserInfo apis are not currently used in CRD.
This also adds remoting.Identity.callWithNewToken, which is similar to
callWithToken except that it always uses a fresh token.
BUG=
Review URL: https://codereview.chromium.org/
714433003
Cr-Commit-Position: refs/heads/master@{#303680}