X87: [es6] Fix invalid ToString in implementation of ToName.

port 09626525 (r30957).

original commit message:

BUG=

Review URL: https://codereview.chromium.org/1370283003

Cr-Commit-Position: refs/heads/master@{#30988}

src/full-codegen/x87/full-codegen-x87.cc

@@ -3695,8 +3695,8 @@ void FullCodeGenerator::EmitToName(CallRuntime* expr) {
   __ CmpObjectType(eax, LAST_NAME_TYPE, ecx);
   __ j(below_equal, &done_convert, Label::kNear);
   __ bind(&convert);
-  ToStringStub stub(isolate());
-  __ CallStub(&stub);
+  __ Push(eax);
+  __ CallRuntime(Runtime::kToName, 1);
   __ bind(&done_convert);
   context()->Plug(eax);
 }