[es6] Partially implement Reflect.preventExtensions.

src/runtime/runtime-scopes.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/runtime/runtime-utils.h"
 
 #include "src/accessors.h"
 #include "src/arguments.h"
 #include "src/frames-inl.h"
 #include "src/isolate-inl.h"
@@ skipping 846 matching lines @@
           break;
         }
         case TEMPORARY:
         case DYNAMIC:
         case DYNAMIC_GLOBAL:
         case DYNAMIC_LOCAL:
           UNREACHABLE();
       }
     }
 
-    JSObject::PreventExtensions(module).Assert();
+    if (JSObject::PreventExtensions(module, THROW_ON_ERROR).IsNothing())
+      DCHECK(false);
   }
 
   DCHECK(!isolate->has_pending_exception());
   return isolate->heap()->undefined_value();
 }
 
 
 RUNTIME_FUNCTION(Runtime_DeleteLookupSlot) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 2);
@@ skipping 288 matching lines @@
 
   // Lookup in the initial Object.prototype object.
   Handle<Object> result;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
       isolate, result,
       Object::GetProperty(isolate->initial_object_prototype(), key));
   return *result;
 }
 }  // namespace internal
 }  // namespace v8