[api] Prototype WeakRef implementation

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index bc43b28fbf4998c305766f408ae3a0fa47a6cd54..3a01f281dc564a2b41396cfb8848d020214b9cd8 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -2697,6 +2697,10 @@ void JSObject::JSObjectShortPrint(StringStream* accumulator) {
       accumulator->Add("<JSWeakSet>");
       break;
     }
+    case JS_WEAK_REF_TYPE: {
+      accumulator->Add("<JSWeakRef>");
+      break;
+    }
     case JS_REGEXP_TYPE: {
       accumulator->Add("<JSRegExp");
       JSRegExp* regexp = JSRegExp::cast(this);
@@ -12789,6 +12793,7 @@ bool CanSubclassHaveInobjectProperties(InstanceType instance_type) {
     case JS_VALUE_TYPE:
     case JS_WEAK_MAP_TYPE:
     case JS_WEAK_SET_TYPE:
+    case JS_WEAK_REF_TYPE:
       return true;
 
     case BYTECODE_ARRAY_TYPE:
@@ -19200,6 +19205,31 @@ Handle<JSArray> JSWeakCollection::GetEntries(Handle<JSWeakCollection> holder,
   return isolate->factory()->NewJSArrayWithElements(entries);
 }
 
+void JSWeakRef::Initialize(Handle<JSWeakRef> weak_ref,
+                                  Isolate* isolate,
+                                  Handle<JSObject> target,
+                                  Handle<JSFunction> executor,
+                                  Handle<Object> holdings) {
+  isolate->factory()->InitJSWeakRef(weak_ref, target, executor, holdings);
+}
+
+Handle<HeapObject> JSWeakRef::Value(Handle<JSWeakRef> weak_ref,
+                                  Isolate* isolate) {
+  if (weak_ref->target() == nullptr || weak_ref->target()->cleared()) {
+    return isolate->factory()->null_value();
+  }
+  weak_ref->set_held(true);
+  return Handle<HeapObject>(
+    reinterpret_cast<HeapObject*>(weak_ref->target()->value()));
+}
+
+void JSWeakRef::Clear(Handle<JSWeakRef> weak_ref,
+                                  Isolate* isolate) {
+  weak_ref->set_executor(nullptr);
+  weak_ref->set_holdings(nullptr);
+  weak_ref->set_target(nullptr);
+}
+
 // Check if there is a break point at this source position.
 bool DebugInfo::HasBreakPoint(int source_position) {
   // Get the break point info object for this code offset.