Fix flag to switch write protection of code pages on/off.

runtime/vm/virtual_memory.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_VIRTUAL_MEMORY_H_
 #define VM_VIRTUAL_MEMORY_H_
 
 #include "platform/utils.h"
 #include "vm/globals.h"
 #include "vm/memory_region.h"
 
 namespace dart {
 
 class VirtualMemory {
  public:
-  // Read-write-execute is not available because it is never used.
   enum Protection {
     kNoAccess,
     kReadOnly,
     kReadWrite,
     kReadExecute,
+    kReadWriteExecute
   };
 
   // The reserved memory is unmapped on destruction.
   ~VirtualMemory();
 
   uword start() const { return region_.start(); }
   uword end() const { return region_.end(); }
   void* address() const { return region_.pointer(); }
   intptr_t size() const { return region_.size(); }
 
@@ skipping 58 matching lines @@
   void* reserved_pointer_;
 
   static uword page_size_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(VirtualMemory);
 };
 
 }  // namespace dart
 
 #endif  // VM_VIRTUAL_MEMORY_H_