[es6] fix nested object literals with computed property names

src/ast.cc

Index: src/ast.cc
diff --git a/src/ast.cc b/src/ast.cc
index 624d462323a9574c278af3e01a240976509239ac..92be8e1952f82d2d251a81b65eff675cd6cb3df1 100644
--- a/src/ast.cc
+++ b/src/ast.cc
@@ -433,7 +433,8 @@ void ObjectLiteral::BuildConstantProperties(Isolate* isolate) {
 
   int position = 0;
   // Accumulate the value in local variables and store it at the end.
-  bool is_simple = true;
+  // If computed property names are used, the literal is never simple.
+  bool is_simple = !has_computed_property_names();
   int depth_acc = 1;
   uint32_t max_element_index = 0;
   uint32_t elements = 0;