Properly disable ES6 generator support for TurboFan.

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index 501f2fd4435d9a3661388e850fbc9067dccfbda4..afe370ee5987a894c4dda100fdb5811cc0008e6e 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -15268,8 +15268,6 @@ RUNTIME_FUNCTION_RETURN_PAIR(Runtime_ForInNext) {
   }
 
 U(IsStringWrapperSafeForDefaultValueOf)
-U(GeneratorNext)
-U(GeneratorThrow)
 U(DebugBreakInOptimizedCode)
 
 #undef U
@@ -15500,6 +15498,18 @@ RUNTIME_FUNCTION(RuntimeReference_FastAsciiArrayJoin) {
 }
 
 
+RUNTIME_FUNCTION(RuntimeReference_GeneratorNext) {
+  UNREACHABLE();  // Optimization disabled in SetUpGenerators().
+  return NULL;
+}
+
+
+RUNTIME_FUNCTION(RuntimeReference_GeneratorThrow) {
+  UNREACHABLE();  // Optimization disabled in SetUpGenerators().
+  return NULL;
+}
+
+
 RUNTIME_FUNCTION(RuntimeReference_ClassOf) {
   SealHandleScope shs(isolate);
   DCHECK(args.length() == 1);