use origin instead of session_id in detecting duplicate EME permission request
The same origin can create a lot of sessions, using session id will generate a lot of duplicate permission requests from a single origin.
This change fixes the behavior by using the origin url.
It also removed the group_id in PermissionRequestId as it is no longer used.
BUG=373641
Review URL: https://codereview.chromium.org/
289023003
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@273457 0039d316-1c4b-4281-b951-d872f2087c98