Make the serialization of IPC::Messages inside other IPC::Messages independent

ipc/ipc_message_utils.cc

Index: ipc/ipc_message_utils.cc
diff --git a/ipc/ipc_message_utils.cc b/ipc/ipc_message_utils.cc
index a8392cf5c5d0354ba07d7ce6b25149cfc60f930a..66a68775ce1124a91a34d33bee671f6173c16f69 100644
--- a/ipc/ipc_message_utils.cc
+++ b/ipc/ipc_message_utils.cc
@@ -730,22 +730,43 @@ void ParamTraits<LogData>::Log(const param_type& p, std::string* l) {
 }
 
 void ParamTraits<Message>::Write(Message* m, const Message& p) {
-  DCHECK(p.size() <= INT_MAX);
-  int message_size = static_cast<int>(p.size());
-  m->WriteInt(message_size);
-  m->WriteData(reinterpret_cast<const char*>(p.data()), message_size);
+#if defined(OS_POSIX)
+  // We don't serialize the file descriptors in the nested message, so there
+  // better not be any.
+  DCHECK(!p.HasFileDescriptors());
+#endif
+
+  // Don't just write out the message. This is used to send messages between
+  // NaCl (Posix environment) and the browser (could be on Windows). The message
+  // header formats differ between these systems (so does handle sharing, but
+  // we already asserted we don't have any handles). So just write out the
+  // parts of the header we use.
+  //
+  // Be careful also to use only explicitly-sized types. The NaCl environment
+  // could be 64-bit and the host browser could be 32-bits. The nested message
+  // may or may not be safe to send between 32-bit and 64-bit systems, but we
+  // leave that up to the code sending the message to ensure.
+  m->WriteUInt32(static_cast<uint32>(p.routing_id()));
+  m->WriteUInt32(p.type());
+  m->WriteUInt32(p.flags());
+  m->WriteData(p.payload(), static_cast<uint32>(p.payload_size()));
 }
 
 bool ParamTraits<Message>::Read(const Message* m, PickleIterator* iter,
                                 Message* r) {
-  int size;
-  if (!m->ReadInt(iter, &size))
+  uint32 routing_id, type, flags;
+  if (!m->ReadUInt32(iter, &routing_id) ||
+      !m->ReadUInt32(iter, &type) ||
+      !m->ReadUInt32(iter, &flags))
     return false;
-  const char* data;
-  if (!m->ReadData(iter, &data, &size))
+
+  int payload_size;
+  const char* payload;
+  if (!m->ReadData(iter, &payload, &payload_size))
     return false;
-  *r = Message(data, size);
-  return true;
+
+  r->SetHeaderValues(static_cast<int32>(routing_id), type, flags);
+  return r->WriteBytes(payload, payload_size);
 }
 
 void ParamTraits<Message>::Log(const Message& p, std::string* l) {