[proxies] Make Object.{isFrozen,isSealed} behave correctly for proxies.

src/runtime/runtime-object.cc

Index: src/runtime/runtime-object.cc
diff --git a/src/runtime/runtime-object.cc b/src/runtime/runtime-object.cc
index 674cc89076586a540d417c29ce102b8f3acdf4e2..4441f47aaa2d0ad69184f4d1692bf19857ca1be4 100644
--- a/src/runtime/runtime-object.cc
+++ b/src/runtime/runtime-object.cc
@@ -343,6 +343,17 @@ RUNTIME_FUNCTION(Runtime_ObjectFreeze) {
 }
 
 
+RUNTIME_FUNCTION(Runtime_ObjectIsFrozen) {
+  HandleScope scope(isolate);
+  DCHECK(args.length() == 1);
+  CONVERT_ARG_HANDLE_CHECKED(JSReceiver, object, 0);
+
+  Maybe<bool> result = JSReceiver::TestIntegrityLevel(object, FROZEN);
+  MAYBE_RETURN(result, isolate->heap()->exception());
+  return isolate->heap()->ToBoolean(result.FromJust());
+}
+
+
 RUNTIME_FUNCTION(Runtime_ObjectSeal) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 1);
@@ -355,6 +366,17 @@ RUNTIME_FUNCTION(Runtime_ObjectSeal) {
 }
 
 
+RUNTIME_FUNCTION(Runtime_ObjectIsSealed) {
+  HandleScope scope(isolate);
+  DCHECK(args.length() == 1);
+  CONVERT_ARG_HANDLE_CHECKED(JSReceiver, object, 0);
+
+  Maybe<bool> result = JSReceiver::TestIntegrityLevel(object, SEALED);
+  MAYBE_RETURN(result, isolate->heap()->exception());
+  return isolate->heap()->ToBoolean(result.FromJust());
+}
+
+
 RUNTIME_FUNCTION(Runtime_LoadGlobalViaContext) {
   HandleScope scope(isolate);
   DCHECK_EQ(1, args.length());