Fix global object check in %IsObserved and %SetIsObserved.

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index 38f77d07137eb06acec574d67d409cdfca073cd1..803bb909c797ba9951dab58a50bd87369b29d3bd 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -12827,7 +12827,7 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_IsObserved) {
   CONVERT_ARG_CHECKED(JSReceiver, obj, 0);
   if (obj->IsJSGlobalProxy()) {
     Object* proto = obj->GetPrototype();
-    if (obj->IsNull()) return isolate->heap()->false_value();
+    if (proto->IsNull()) return isolate->heap()->false_value();
     ASSERT(proto->IsJSGlobalObject());
     obj = JSReceiver::cast(proto);
   }
@@ -12842,7 +12842,7 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_SetIsObserved) {
   CONVERT_BOOLEAN_ARG_CHECKED(is_observed, 1);
   if (obj->IsJSGlobalProxy()) {
     Object* proto = obj->GetPrototype();
-    if (obj->IsNull()) return isolate->heap()->undefined_value();
+    if (proto->IsNull()) return isolate->heap()->undefined_value();
     ASSERT(proto->IsJSGlobalObject());
     obj = JSReceiver::cast(proto);
   }