Implement MediaDrm offline license support in Widevine hidl service.

Merged from http://go/wvgerrit/69723.

The new APIs are getOfflineLicenseIds, getOfflineLicenseState and
removeOfflineLicense. These methods are currently stubbed out in
Widevine hidl service. This CL completes the implementation.

Test: unit tests - libwvdrmdrmplugin_hidl_test

Test: GTS
  --test com.google.android.media.gts.MediaDrmTest#testWidevineApi29

bug: 117570686
Change-Id: I96ffb75f453e36e931effefd3664b5faa8d69d30

libwvdrmengine/cdm/include/wv_content_decryption_module.h

@@ -147,6 +147,26 @@ class WvContentDecryptionModule : public android::RefBase, public TimerHandler {
   virtual CdmResponseType GetDecryptHashError(const CdmSessionId& session_id,
                                               std::string* hash_error_string);
 
+  // Return the list of key_set_ids stored on the current (origin-specific)
+  // file system.
+  virtual CdmResponseType ListStoredLicenses(
+      CdmSecurityLevel security_level,
+      const CdmIdentifier& identifier,
+      std::vector<CdmKeySetId>* key_set_ids);
+
+  // Retrieve offline license state using key_set_id.
+  virtual CdmResponseType GetOfflineLicenseState(
+      const CdmKeySetId& key_set_id,
+      CdmSecurityLevel security_level,
+      const CdmIdentifier& identifier,
+      CdmOfflineLicenseState* licenseState);
+
+  // Remove offline license using key_set_id.
+  virtual CdmResponseType RemoveOfflineLicense(
+      const CdmKeySetId& key_set_id,
+      CdmSecurityLevel security_level,
+      const CdmIdentifier& identifier);
+
  private:
   struct CdmInfo {
     CdmInfo();