[strong] class objects created in strong mode have their prototype frozen

src/x64/full-codegen-x64.cc

 // 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.
 
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
@@ skipping 2549 matching lines @@
       default:
         UNREACHABLE();
     }
   }
 
   // prototype
   __ CallRuntime(Runtime::kToFastProperties, 1);
 
   // constructor
   __ CallRuntime(Runtime::kToFastProperties, 1);
+
+  if (is_strong(language_mode())) {
+    __ movp(scratch,
+            FieldOperand(rax, JSFunction::kPrototypeOrInitialMapOffset));
+    __ Push(rax);
+    __ Push(scratch);
+    __ CallRuntime(Runtime::kObjectFreeze, 1);
+    // TODO(conradw): It would be more efficient to define the properties with
+    // the right attributes the first time round.
+    __ CallRuntime(Runtime::kObjectFreeze, 1);
+  }
 }
 
 
 void FullCodeGenerator::EmitBinaryOp(BinaryOperation* expr, Token::Value op) {
   __ Pop(rdx);
   Handle<Code> code =
       CodeFactory::BinaryOpIC(isolate(), op, strength(language_mode())).code();
   JumpPatchSite patch_site(masm_);    // unbound, signals no inlined smi code.
   CallIC(code, expr->BinaryOperationFeedbackId());
   patch_site.EmitPatchInfo();
@@ skipping 2936 matching lines @@
             Assembler::target_address_at(call_target_address,
                                          unoptimized_code));
   return OSR_AFTER_STACK_CHECK;
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64