chromeos: Make dbus::MessageReader memory ownership explicit

chromeos/dbus/session_manager_client.cc

Index: chromeos/dbus/session_manager_client.cc
diff --git a/chromeos/dbus/session_manager_client.cc b/chromeos/dbus/session_manager_client.cc
index 7def286cda74cd1d982eea943fa10d92a0d5f8b3..c01f28f759002025b96366e910dc75f74e3c946b 100644
--- a/chromeos/dbus/session_manager_client.cc
+++ b/chromeos/dbus/session_manager_client.cc
@@ -403,14 +403,14 @@ class SessionManagerClientImpl : public SessionManagerClient {
       return;
     }
     dbus::MessageReader reader(response);
-    uint8* values = NULL;
+    const uint8* values = NULL;
     size_t length = 0;
     if (!reader.PopArrayOfBytes(&values, &length)) {
       LOG(ERROR) << "Invalid response: " << response->ToString();
       return;
     }
     // static_cast does not work due to signedness.
-    extracted->assign(reinterpret_cast<char*>(values), length);
+    extracted->assign(reinterpret_cast<const char*>(values), length);
   }
 
   // Called when kSessionManagerRetrievePolicy or