Fix more GC unsafe places

src/bootstrapper.cc

Index: src/bootstrapper.cc
diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index f2e31c0f538fac3666bbc788ad5d0bc66c3be43c..aa8d8e5ac22acc53282278b28413dedd5dc90e3c 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -1064,8 +1064,11 @@ bool Genesis::InstallNatives() {
   // global object.
   static const PropertyAttributes attributes =
       static_cast<PropertyAttributes>(READ_ONLY | DONT_DELETE);
-  SetProperty(builtins, Factory::LookupAsciiSymbol("global"),
-              Handle<Object>(global_context()->global()), attributes);
+  Handle<String> global_symbol = Factory::LookupAsciiSymbol("global");
+  SetProperty(builtins,
+              global_symbol,
+              Handle<Object>(global_context()->global()),
+              attributes);
 
   // Setup the reference from the global object to the builtins object.
   JSGlobalObject::cast(global_context()->global())->set_builtins(*builtins);