Made iteration of global handles more efficient on scavenges.

src/heap-profiler.cc

Index: src/heap-profiler.cc
diff --git a/src/heap-profiler.cc b/src/heap-profiler.cc
index 7f7cd7f1691ed08d05259ef6a40330c68afef6d2..bd1cd2d9cf01a9d06a910e5df79f103cd25d4e63 100644
--- a/src/heap-profiler.cc
+++ b/src/heap-profiler.cc
@@ -536,7 +536,7 @@ RetainerHeapProfile::RetainerHeapProfile()
     : zscope_(DELETE_ON_EXIT) {
   JSObjectsCluster roots(JSObjectsCluster::ROOTS);
   ReferencesExtractor extractor(roots, this);
-  Heap::IterateRoots(&extractor);
+  Heap::IterateRoots(&extractor, VISIT_ONLY_STRONG);
 }