Implement Method to Release Licenses Without a Server Roundtrip

Merge from Widevine repo of http://go/wvgerrit/52480

Partners have asked for a way to release offline licenses without
using a release message. This is typically used by cable partners who
are caching licenses ahead of time and do not care about usage
statistics.

As part of implementing this request, CdmSession::DeleteLicense() was
renamed to reflect that it only deletes the *files* associated with a
license, and a new CdmSession::DeleteLicense() has been written that
also cleans up other related data.

Bug: 77955334
Test: CE CDM Unit Tests
Test: tested as part of http://go/ag/4674759
Change-Id: I00d6e20935c5fecb3ac9be6757c0f191d85c6bd6

libwvdrmengine/cdm/core/include/cdm_engine.h

@@ -113,8 +113,18 @@ class CdmEngine {
   virtual CdmResponseType RestoreKey(const CdmSessionId& session_id,
                                      const CdmKeySetId& key_set_id);
 
+  // This method releases the crypto resources and policy resources associated
+  // with the given session. This renders the session largely useless. It is
+  // preferable to close the session outright. This method does not delete any
+  // stored offline data associated with the session.
   virtual CdmResponseType RemoveKeys(const CdmSessionId& session_id);
 
+  // This method removes all offline data associated with the session, such as
+  // offline keys and usage info. It should be used with care, as it deletes the
+  // info immediately and without using a release message, so the server is not
+  // able to receive usage info or track releases for offline licenses.
+  virtual CdmResponseType RemoveLicense(const CdmSessionId& session_id);
+
   // Construct valid renewal request for the current session keys.
   virtual CdmResponseType GenerateRenewalRequest(
       const CdmSessionId& session_id, CdmKeyRequest* key_request);