Optimize functions on a second thread.

src/handles-inl.h

Index: src/handles-inl.h
diff --git a/src/handles-inl.h b/src/handles-inl.h
index a5c81cec56f1d0056be0d1066683fc27432a4362..3665a3ed1c6573f6e51982ccb3d3d69e2639a629 100644
--- a/src/handles-inl.h
+++ b/src/handles-inl.h
@@ -149,8 +149,11 @@ T** HandleScope::CreateHandle(T* value, Isolate* isolate) {
 
 #ifdef DEBUG
 inline NoHandleAllocation::NoHandleAllocation() {
+  Isolate* isolate = Isolate::Current();
   v8::ImplementationUtilities::HandleScopeData* current =
-      Isolate::Current()->handle_scope_data();
+      isolate->handle_scope_data();
+
+  ASSERT(!isolate->optimizing_compiler_thread()->IsOptimizerThread());
 
   // Shrink the current handle scope to make it impossible to do
   // handle allocations without an explicit handle scope.