Add WeakMap to v8.h

test/cctest/test-weakmaps.cc

Index: test/cctest/test-weakmaps.cc
diff --git a/test/cctest/test-weakmaps.cc b/test/cctest/test-weakmaps.cc
index 6c19cb8e47d5caa1c92b96d9704e23653424b9e5..c3b0c2efd1b3596cff4fefb3500b3762fcd3c20d 100644
--- a/test/cctest/test-weakmaps.cc
+++ b/test/cctest/test-weakmaps.cc
@@ -42,10 +42,7 @@ static Isolate* GetIsolateFrom(LocalContext* context) {
 
 
 static Handle<JSWeakMap> AllocateJSWeakMap(Isolate* isolate) {
-  Factory* factory = isolate->factory();
-  Handle<Map> map = factory->NewMap(JS_WEAK_MAP_TYPE, JSWeakMap::kSize);
-  Handle<JSObject> weakmap_obj = factory->NewJSObjectFromMap(map);
-  Handle<JSWeakMap> weakmap(JSWeakMap::cast(*weakmap_obj));
+  Handle<JSWeakMap> weakmap = isolate->factory()->NewJSWeakMap();
   // Do not leak handles for the hash table, it would make entries strong.
   {
     HandleScope scope(isolate);
@@ -58,11 +55,7 @@ static Handle<JSWeakMap> AllocateJSWeakMap(Isolate* isolate) {
 static void PutIntoWeakMap(Handle<JSWeakMap> weakmap,
                            Handle<JSObject> key,
                            Handle<Object> value) {
-  Handle<ObjectHashTable> table = ObjectHashTable::Put(
-      Handle<ObjectHashTable>(ObjectHashTable::cast(weakmap->table())),
-      Handle<JSObject>(JSObject::cast(*key)),
-      value);
-  weakmap->set_table(*table);
+  Runtime::WeakCollectionSet(weakmap, key, value);
 }
 
 static int NumberOfWeakCalls = 0;