Reuse base class IsCurrentThread

Change-Id: Ie185983d7cf546def5e310493c7b26f520bbe08d
Reviewed-on: https://gerrit.libreoffice.org/71344
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

vcl/win/app/salinst.cxx

@@ -213,8 +213,7 @@ void ImplSalYieldMutexRelease()
 bool SalYieldMutex::IsCurrentThread() const
 {
     if ( !GetSalData()->mpInstance->m_nNoYieldLock )
-        // For the Windows backend, the LO identifier is the system thread ID
-        return m_nThreadId == GetCurrentThreadId();
+        return SolarMutex::IsCurrentThread();
     else
         return GetSalData()->mpInstance->IsMainThread();
 }