[runtime] Only muck with prototype dependencies for prototypes

src/objects.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/objects.h"
 
 #include <cmath>
 #include <iomanip>
 #include <sstream>
 
@@ skipping 3051 matching lines @@
     object->Print(os);
   }
 #endif
 }
 
 }  // namespace
 
 void JSObject::MigrateToMap(Handle<JSObject> object, Handle<Map> new_map,
                             int expected_additional_properties) {
   if (object->map() == *new_map) return;
-  // If this object is a prototype (the callee will check), invalidate any
-  // prototype chains involving it.
-  InvalidatePrototypeChains(object->map());
   Handle<Map> old_map(object->map());
+  if (old_map->is_prototype_map()) {
+    // If this object is a prototype (the callee will check), invalidate any
+    // prototype chains involving it.
+    InvalidatePrototypeChains(object->map());
 
-  // If the map was registered with its prototype before, ensure that it
-  // registers with its new prototype now. This preserves the invariant that
-  // when a map on a prototype chain is registered with its prototype, then
-  // all prototypes further up the chain are also registered with their
-  // respective prototypes.
-  UpdatePrototypeUserRegistration(old_map, new_map, new_map->GetIsolate());
+    // If the map was registered with its prototype before, ensure that it
+    // registers with its new prototype now. This preserves the invariant that
+    // when a map on a prototype chain is registered with its prototype, then
+    // all prototypes further up the chain are also registered with their
+    // respective prototypes.
+    UpdatePrototypeUserRegistration(old_map, new_map, new_map->GetIsolate());
+  }
 
   if (old_map->is_dictionary_map()) {
     // For slow-to-fast migrations JSObject::MigrateSlowToFast()
     // must be used instead.
     CHECK(new_map->is_dictionary_map());
 
     // Slow-to-slow migration is trivial.
     object->set_map(*new_map);
   } else if (!new_map->is_dictionary_map()) {
     MigrateFastToFast(object, new_map);
@@ skipping 16791 matching lines @@
   if (cell->value() != *new_value) {
     cell->set_value(*new_value);
     Isolate* isolate = cell->GetIsolate();
     cell->dependent_code()->DeoptimizeDependentCodeGroup(
         isolate, DependentCode::kPropertyCellChangedGroup);
   }
 }
 
 }  // namespace internal
 }  // namespace v8