Add Provisioning 4 support

Widevine provisioning 4 support is added in this patch.

plugin/include/widevine_media_cas_plugin.h

@@ -91,7 +91,7 @@ class WidevineCasPlugin : public CasPlugin, public CasEventListener {
       std::unique_ptr<WidevineCas> widevine_cas_api) {
     widevine_cas_api_ = std::move(widevine_cas_api);
   }
-  WidevineCasPlugin(){};
+  WidevineCasPlugin() {};
 
  private:
   // |sessionId| is nullptr if the event is not a session event.
@@ -107,6 +107,7 @@ class WidevineCasPlugin : public CasPlugin, public CasEventListener {
   CasStatus HandleAssignLicenseID(const CasData& license_id);
   CasStatus HandlePluginVersionQuery();
   CasStatus HandleEntitlementPeriodUpdateResponse(const CasData& response);
+  status_t provisionInternal();
 
   // Returns true if the device has been provisioned with a device certificate.
   bool is_provisioned() const;