Run Crankshaft on a separate thread.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 4fd29ad56227d368d2ebb0773c566f6cba3909b0..1375c8d23b66c47af03ebdda67890fe84f81f70f 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -5782,6 +5782,10 @@ class JSFunction: public JSObject {
   // recompiled the next time it is executed.
   void MarkForLazyRecompilation();
 
+  // Compile this function on the separate compiler thread.  Asserts
+  // FLAG_concurrrent_crankshaft
+  void CompileConcurrently();
+
   // Helpers to compile this function.  Returns true on success, false on
   // failure (e.g., stack overflow during compilation).
   static bool CompileLazy(Handle<JSFunction> function,