Pass signin_scoped_device_id to DeviceInfoSpecifics.
I'm adding signin_scoped_device_id to DeviceInfoSpecifics.
This value is available from SigninClient, the rest of code is to pass
value from syncBackendHostImpl where SigninClient is availble to
SyncedDeviceTracker where value is passed to protobuf.
Also there is small change to how commandline flag is handled.
BUG=382968
R=rlarocque@chromium.org
Review URL: https://codereview.chromium.org/
395013002
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@284234 0039d316-1c4b-4281-b951-d872f2087c98