Avoid trusting the length encoded in the Snapshot if there is an

runtime/vm/message.h

 // Copyright (c) 2011, 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_MESSAGE_H_
 #define VM_MESSAGE_H_
 
 #include "vm/thread.h"
 
 // Duplicated from dart_api.h to avoid including the whole header.
@@ skipping 14 matching lines @@
 
   // A port number which is never used.
   static const Dart_Port kIllegalPort = 0;
 
   // A new message to be sent between two isolates. The data handed to this
   // message will be disposed by calling free() once the message object is
   // being destructed (after delivery or when the receiving port is closed).
   //
   // If reply_port is kIllegalPort, then there is no reply port.
   Message(Dart_Port dest_port, Dart_Port reply_port,
-          uint8_t* data, Priority priority)
+          uint8_t* data, intptr_t len, Priority priority)
       : next_(NULL),
         dest_port_(dest_port),
         reply_port_(reply_port),
         data_(data),
+        len_(len),
         priority_(priority) {}
   ~Message() {
     free(data_);
   }
 
   Dart_Port dest_port() const { return dest_port_; }
   Dart_Port reply_port() const { return reply_port_; }
   uint8_t* data() const { return data_; }
+  intptr_t len() const { return len_; }
   Priority priority() const { return priority_; }
 
   bool IsOOB() const { return priority_ == Message::kOOBPriority; }
 
  private:
   friend class MessageQueue;
 
   Message* next_;
   Dart_Port dest_port_;
   Dart_Port reply_port_;
   uint8_t* data_;
+  intptr_t len_;
   Priority priority_;
 
   DISALLOW_COPY_AND_ASSIGN(Message);
 };
 
 // There is a message queue per isolate.
 class MessageQueue {
  public:
   MessageQueue();
   ~MessageQueue();
@@ skipping 12 matching lines @@
 
   Message* head_;
   Message* tail_;
 
   DISALLOW_COPY_AND_ASSIGN(MessageQueue);
 };
 
 }  // namespace dart
 
 #endif  // VM_MESSAGE_H_