[api] Prototype WeakRef implementation

src/runtime/runtime-collections.cc

Index: src/runtime/runtime-collections.cc
diff --git a/src/runtime/runtime-collections.cc b/src/runtime/runtime-collections.cc
index 214ce1c4e6cf590b3d54fb237a8b51758c44a764..97c7a0b5e88c99b47c0f7498ac822ae3f79beddb 100644
--- a/src/runtime/runtime-collections.cc
+++ b/src/runtime/runtime-collections.cc
@@ -325,5 +325,33 @@ RUNTIME_FUNCTION(Runtime_GetWeakSetValues) {
   CHECK(max_values >= 0);
   return *JSWeakCollection::GetEntries(holder, max_values);
 }
+
+RUNTIME_FUNCTION(Runtime_WeakRefInitialize) {
+  HandleScope scope(isolate);
+  DCHECK_EQ(3, args.length());
+  CONVERT_ARG_HANDLE_CHECKED(JSWeakRef, weak_ref, 0);
+  CONVERT_ARG_HANDLE_CHECKED(JSObject, target, 1);
+  CONVERT_ARG_HANDLE_CHECKED(JSFunction, executor, 2);
+  CONVERT_ARG_HANDLE_CHECKED(Object, holdings, 3);
+  JSWeakRef::Initialize(weak_ref, isolate, target, executor, holdings);
+  return *weak_ref;
+}
+
+RUNTIME_FUNCTION(Runtime_WeakRefValue) {
+  HandleScope scope(isolate);
+  DCHECK_EQ(1, args.length());
+  CONVERT_ARG_HANDLE_CHECKED(JSWeakRef, weak_ref, 0);
+  Handle<Object> value = JSWeakRef::Value(weak_ref, isolate);
+  weak_ref->set_held(true);
+  return *value;
+}
+
+RUNTIME_FUNCTION(Runtime_WeakRefClear) {
+  HandleScope scope(isolate);
+  DCHECK_EQ(1, args.length());
+  CONVERT_ARG_HANDLE_CHECKED(JSWeakRef, weak_ref, 0);
+  JSWeakRef::Clear(weak_ref, isolate);
+  return isolate->heap()->undefined_value();
+}
 }  // namespace internal
 }  // namespace v8