Tweak the TurboFan pipeline for stub compilation.

src/runtime/runtime-strings.cc

Index: src/runtime/runtime-strings.cc
diff --git a/src/runtime/runtime-strings.cc b/src/runtime/runtime-strings.cc
index 89b0d2bfa8fe08e430a19f65397f0d15a46604f7..a4b2a9afb27050e73695cbad880ed4046b3acf2f 100644
--- a/src/runtime/runtime-strings.cc
+++ b/src/runtime/runtime-strings.cc
@@ -1301,5 +1301,13 @@ RUNTIME_FUNCTION(Runtime_IsStringWrapperSafeForDefaultValueOf) {
   UNIMPLEMENTED();
   return NULL;
 }
+
+
+RUNTIME_FUNCTION(Runtime_StringGetLength) {
+  HandleScope scope(isolate);
+  DCHECK(args.length() == 1);
+  CONVERT_ARG_HANDLE_CHECKED(String, s, 0);
+  return Smi::FromInt(s->length());
+}
 }
 }  // namespace v8::internal