Sign unused renewal so that offline renewal may be loaded

Merge from Widevine repo of http://go/wvgerrit/105347

When reloading an offline license that has an offline renewal, we sign
a unused renewal so that the ODK library can update its clock values.

Test: WV unit/integration tests, GtsMediaTestCases tests
Bug: 166131956
Change-Id: Ib1445fd85222489f21221e00729d4989cb49a331

libwvdrmengine/cdm/core/include/license.h

@@ -123,6 +123,11 @@ class CdmLicense {
       const std::string& mac_key, const std::vector<CryptoKey>& key_array,
       const video_widevine::License& license);
 
+  // Prepare to reload a key update message. Some special code is needed to work
+  // around b/166010609.
+  // TODO(b/166007195): Remove this.
+  CdmResponseType PrepareKeyUpdateReload(CdmSession* cdm_session);
+
   CdmResponseType HandleNewEntitledKeys(
       const std::vector<WidevinePsshData_EntitledKey>& wrapped_keys);