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

src/compiler/ast-graph-builder.cc

 // Copyright 2014 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/compiler/ast-graph-builder.h"
 
 #include "src/compiler.h"
 #include "src/compiler/ast-loop-assignment-analyzer.h"
 #include "src/compiler/control-builders.h"
 #include "src/compiler/js-type-feedback.h"
@@ skipping 1625 matching lines @@
     }
   }
 
   // Transform both the class literal and the prototype to fast properties.
   const Operator* op = javascript()->CallRuntime(Runtime::kToFastProperties, 1);
   NewNode(op, environment()->Pop());  // prototype
   NewNode(op, environment()->Pop());  // literal
   if (is_strong(language_mode())) {
     // TODO(conradw): It would be more efficient to define the properties with
     // the right attributes the first time round.
+    // Freeze the prototype.
+    proto =
+        NewNode(javascript()->CallRuntime(Runtime::kObjectFreeze, 1), proto);
+    // Freezing the prototype should never deopt.
+    PrepareFrameState(proto, BailoutId::None());
+    // Freeze the constructor.
     literal =
         NewNode(javascript()->CallRuntime(Runtime::kObjectFreeze, 1), literal);
-    // Freezing the class object should never deopt.
+    // Freezing the constructor should never deopt.
     PrepareFrameState(literal, BailoutId::None());
   }
 
   // Assign to class variable.
   if (expr->scope() != NULL) {
     DCHECK_NOT_NULL(expr->class_variable_proxy());
     Variable* var = expr->class_variable_proxy()->var();
     FrameStateBeforeAndAfter states(this, BailoutId::None());
     VectorSlotPair feedback = CreateVectorSlotPair(
         FLAG_vector_stores ? expr->GetNthSlot(store_slot_index++)
@@ skipping 2586 matching lines @@
     // Phi does not exist yet, introduce one.
     value = NewPhi(inputs, value, control);
     value->ReplaceInput(inputs - 1, other);
   }
   return value;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8