Run Crankshaft on a separate thread.

src/factory.cc

Index: src/factory.cc
diff --git a/src/factory.cc b/src/factory.cc
index 6bb7893746d794b7654e1fb7dfd85aaf8f9fe569..ac30f213c9339237f9e483eeeb64f53d64985f8c 100644
--- a/src/factory.cc
+++ b/src/factory.cc
@@ -568,7 +568,10 @@ Handle<JSFunction> Factory::NewFunctionFromSharedFunctionInfo(
       !function_info->is_toplevel() &&
       function_info->allows_lazy_compilation() &&
       !function_info->optimization_disabled()) {
-    result->MarkForLazyRecompilation();
+    if (FLAG_concurrent_crankshaft)
+      result->CompileConcurrently();
+    else
+      result->MarkForLazyRecompilation();
   }
   return result;
 }