Make sure builtin functions don't rely on __proto__.

src/x64/full-codegen-x64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1608 matching lines @@
             Handle<Code> ic = is_classic_mode()
                 ? isolate()->builtins()->StoreIC_Initialize()
                 : isolate()->builtins()->StoreIC_Initialize_Strict();
             CallIC(ic, RelocInfo::CODE_TARGET, key->LiteralFeedbackId());
             PrepareForBailoutForId(key->id(), NO_REGISTERS);
           } else {
             VisitForEffect(value);
           }
           break;
         }
-        // Fall through.
-      case ObjectLiteral::Property::PROTOTYPE:
         __ push(Operand(rsp, 0));  // Duplicate receiver.
         VisitForStackValue(key);
         VisitForStackValue(value);
         if (property->emit_store()) {
           __ Push(Smi::FromInt(NONE));    // PropertyAttributes
           __ CallRuntime(Runtime::kSetProperty, 4);
         } else {
           __ Drop(3);
         }
         break;
+      case ObjectLiteral::Property::PROTOTYPE:
+        __ push(Operand(rsp, 0));  // Duplicate receiver.
+        VisitForStackValue(value);
+        if (property->emit_store()) {
+          __ CallRuntime(Runtime::kSetPrototype, 2);
+        } else {
+          __ Drop(2);
+        }
+        break;
       case ObjectLiteral::Property::GETTER:
         accessor_table.lookup(key)->second->getter = value;
         break;
       case ObjectLiteral::Property::SETTER:
         accessor_table.lookup(key)->second->setter = value;
         break;
     }
   }
 
   // Emit code to define accessors, using only a single call to the runtime for
@@ skipping 2888 matching lines @@
   *context_length = 0;
   return previous_;
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64