[strong] weak classes can't inherit from strong ones

src/runtime/runtime.h

 // Copyright 2012 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.
 
 #ifndef V8_RUNTIME_RUNTIME_H_
 #define V8_RUNTIME_RUNTIME_H_
 
 #include "src/allocation.h"
 #include "src/objects.h"
 #include "src/unicode.h"
@@ skipping 66 matching lines @@
 #define FOR_EACH_INTRINSIC_CLASSES(F)         \
   F(ThrowNonMethodError, 0, 1)                \
   F(ThrowUnsupportedSuperError, 0, 1)         \
   F(ThrowConstructorNonCallableError, 0, 1)   \
   F(ThrowArrayNotSubclassableError, 0, 1)     \
   F(ThrowStaticPrototypeError, 0, 1)          \
   F(ThrowIfStaticPrototype, 1, 1)             \
   F(ToMethod, 2, 1)                           \
   F(HomeObjectSymbol, 0, 1)                   \
   F(DefineClass, 5, 1)                        \
-  F(DefineClassStrong, 5, 1)                  \
   F(FinalizeClassDefinition, 2, 1)            \
   F(DefineClassMethod, 3, 1)                  \
   F(ClassGetSourceCode, 1, 1)                 \
   F(LoadFromSuper, 4, 1)                      \
   F(LoadKeyedFromSuper, 4, 1)                 \
   F(StoreToSuper_Strict, 4, 1)                \
   F(StoreToSuper_Sloppy, 4, 1)                \
   F(StoreKeyedToSuper_Strict, 4, 1)           \
   F(StoreKeyedToSuper_Sloppy, 4, 1)           \
   F(HandleStepInForDerivedConstructors, 1, 1) \
@@ skipping 1154 matching lines @@
 inline bool Runtime::AtomicIsLockFree(uint32_t size) {
   return size == 1 || size == 2 || size == 4;
 }
 
 #endif
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_RUNTIME_RUNTIME_H_