[es6] Reintroduce the instanceof operator in the backends.

src/full-codegen/x64/full-codegen-x64.cc

Index: src/full-codegen/x64/full-codegen-x64.cc
diff --git a/src/full-codegen/x64/full-codegen-x64.cc b/src/full-codegen/x64/full-codegen-x64.cc
index 74dbdf08ae5141d00101ca26403fa5f02ad7d8f7..28a995ffb88556507c19ab2d3df5921f028f0640 100644
--- a/src/full-codegen/x64/full-codegen-x64.cc
+++ b/src/full-codegen/x64/full-codegen-x64.cc
@@ -3015,12 +3015,6 @@ void FullCodeGenerator::EmitGetSuperConstructor(CallRuntime* expr) {
   context()->Plug(rax);
 }
 
-void FullCodeGenerator::EmitGetOrdinaryHasInstance(CallRuntime* expr) {
-  DCHECK_EQ(0, expr->arguments()->length());
-  __ LoadNativeContextSlot(Context::ORDINARY_HAS_INSTANCE_INDEX, rax);
-  context()->Plug(rax);
-}
-
 void FullCodeGenerator::EmitDebugIsActive(CallRuntime* expr) {
   DCHECK(expr->arguments()->length() == 0);
   ExternalReference debug_is_active =