Count GlobalHandles::PostGarbageCollectionProcessing() as being

in external code so it's visible when running with --trace-gc.

Landed on behalf of James Robinson (jamesr@chromium.org).

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3981 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/heap.cc

@@ -594,6 +594,7 @@ void Heap::PerformGarbageCollection(AllocationSpace space,
 
   if (collector == MARK_COMPACTOR) {
     DisableAssertNoAllocation allow_allocation;
+    GCTracer::ExternalScope scope(tracer);
     GlobalHandles::PostGarbageCollectionProcessing();
   }