Report provider client token

[ Merge of http://go/wvgerrit/71103 ]

A content provider may specify a provider client token in a license.
This is a client token generated by a provider. If present in a license,
they will now be included in a license renewal request.

Bug: 34386290
Test: WV unit/integration tests
Change-Id: I3db303ea4d8b4ff4495393be4015b49e13db2ffc

libwvdrmengine/cdm/core/include/license.h

@@ -84,6 +84,7 @@ class CdmLicense {
 
   CdmResponseType PrepareClientId(
       const CdmAppParameterMap& app_parameters,
+      const std::string& provider_client_token,
       video_widevine::LicenseRequest* license_request);
 
   CdmResponseType PrepareContentId(
@@ -148,6 +149,9 @@ class CdmLicense {
 
   CdmLicenseKeyType license_key_type_;
   RepeatedPtrField<License_KeyContainer> entitlement_keys_;
+
+  std::string provider_client_token_;
+
 #if defined(UNIT_TEST)
   friend class CdmLicenseTestPeer;
 #endif