8061630: G1 iterates over JNIHandles two times

Reviewed-by: mgerdin, brutisso

src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp

@@ -5900,15 +5900,11 @@ void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
   // not copied during the pause.
   process_discovered_references(n_workers);
 
-  // Weak root processing.
-  {
+  if (G1StringDedup::is_enabled()) {
     G1STWIsAliveClosure is_alive(this);
     G1KeepAliveClosure keep_alive(this);
-    JNIHandles::weak_oops_do(&is_alive, &keep_alive);
-    if (G1StringDedup::is_enabled()) {
     G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive);
   }
-  }
 
   _allocator->release_gc_alloc_regions(n_workers, evacuation_info);
   g1_rem_set()->cleanup_after_oops_into_collection_set_do();