Re-initialize drive and metadata_database when RefreshToken is obtained later

(Looks like v1 also has this problem, will make a patch for that too)

BUG=326410
TEST=manual: Launch chrome without signed-in, launch syncfs app (fails),
sign-in and re-launch syncfs app to see it succeeds

Review URL: https://codereview.chromium.org/110003002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@239462 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 239462