Support ES6 weak collections in heap profiler

src/heap-snapshot-generator.cc

Index: src/heap-snapshot-generator.cc
diff --git a/src/heap-snapshot-generator.cc b/src/heap-snapshot-generator.cc
index 87d7819da5be0af475e9b68b6f5a033570cb1ae9..4a847651efdb02daf28acb5196b4b62fcad85c26 100644
--- a/src/heap-snapshot-generator.cc
+++ b/src/heap-snapshot-generator.cc
@@ -1097,6 +1097,10 @@ bool V8HeapExplorer::ExtractReferencesPass1(int entry, HeapObject* obj) {
     ExtractJSGlobalProxyReferences(entry, JSGlobalProxy::cast(obj));
   } else if (obj->IsJSArrayBuffer()) {
     ExtractJSArrayBufferReferences(entry, JSArrayBuffer::cast(obj));
+  } else if (obj->IsJSWeakSet()) {
+    ExtractJSWeakCollectionReferences(entry, JSWeakSet::cast(obj));
+  } else if (obj->IsJSWeakMap()) {
+    ExtractJSWeakCollectionReferences(entry, JSWeakMap::cast(obj));
   } else if (obj->IsJSObject()) {
     ExtractJSObjectReferences(entry, JSObject::cast(obj));
   } else if (obj->IsString()) {
@@ -1256,6 +1260,15 @@ void V8HeapExplorer::ExtractSymbolReferences(int entry, Symbol* symbol) {
 }
 
 
+void V8HeapExplorer::ExtractJSWeakCollectionReferences(
+    int entry, JSWeakCollection* collection) {
+  MarkAsWeakContainer(collection->table());
+  SetInternalReference(collection, entry,
+                       "table", collection->table(),
+                       JSWeakCollection::kTableOffset);
+}
+
+
 void V8HeapExplorer::ExtractContextReferences(int entry, Context* context) {
   if (context == context->declaration_context()) {
     ScopeInfo* scope_info = context->closure()->shared()->scope_info();