[turbofan] Don't lookup private symbols on prototypes.

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 8bbf668949a0ad8ac79a36a706134ed6cb8d9075..42b15fe351fae96b7af341a2884ed8f80f2e1401 100644
--- a/src/compiler/js-native-context-specialization.cc
+++ b/src/compiler/js-native-context-specialization.cc
@@ -449,6 +449,9 @@ bool JSNativeContextSpecialization::ComputePropertyAccessInfo(
       return false;
     }
 
+    // Don't lookup private symbols on the prototype chain.
+    if (name->IsPrivate()) return false;
+
     // Walk up the prototype chain.
     if (!map->prototype()->IsJSObject()) {
       // Perform the implicit ToObject for primitives here.