[turbofan] Create initial map on-demand for F.prototype.

src/compiler/js-native-context-specialization.cc

Index: src/compiler/js-native-context-specialization.cc
diff --git a/src/compiler/js-native-context-specialization.cc b/src/compiler/js-native-context-specialization.cc
index 094e3a1166c79e3fee86883a97e42a53eef057e7..3ee28911a24499b17ffaf7bf61190fc47ddd799d 100644
--- a/src/compiler/js-native-context-specialization.cc
+++ b/src/compiler/js-native-context-specialization.cc
@@ -826,11 +826,11 @@ Reduction JSNativeContextSpecialization::ReduceJSLoadNamed(Node* node) {
         p.name().is_identical_to(factory()->prototype_string())) {
       // Optimize "prototype" property of functions.
       Handle<JSFunction> function = Handle<JSFunction>::cast(m.Value());
-      if (function->has_initial_map()) {
+      if (function->IsConstructor()) {
         // We need to add a code dependency on the initial map of the
         // {function} in order to be notified about changes to the
-        // "prototype" of {function}, so it doesn't make sense to
-        // continue unless deoptimization is enabled.
+        // "prototype" of {function}.
+        JSFunction::EnsureHasInitialMap(function);
         Handle<Map> initial_map(function->initial_map(), isolate());
         dependencies()->AssumeInitialMapCantChange(initial_map);
         Handle<Object> prototype(function->prototype(), isolate());