Add a SetDoNotFragment() method to DatagramSocket, and call this for

net/quic/chromium/quic_stream_factory.cc

Index: net/quic/chromium/quic_stream_factory.cc
diff --git a/net/quic/chromium/quic_stream_factory.cc b/net/quic/chromium/quic_stream_factory.cc
index c1711985e4887f72c074fed495d30288e0ef9c06..14852726a81fc208e15920819adcadfa5772f81f 100644
--- a/net/quic/chromium/quic_stream_factory.cc
+++ b/net/quic/chromium/quic_stream_factory.cc
@@ -67,6 +67,7 @@ enum CreateSessionFailure {
   CREATION_ERROR_CONNECTING_SOCKET,
   CREATION_ERROR_SETTING_RECEIVE_BUFFER,
   CREATION_ERROR_SETTING_SEND_BUFFER,
+  CREATION_ERROR_SETTING_NO_NOT_FRAGMENT,
   CREATION_ERROR_MAX
 };
 
@@ -1729,6 +1730,12 @@ int QuicStreamFactory::ConfigureSocket(DatagramClientSocket* socket,
     return rv;
   }
 
+  rv = socket->SetDoNotFragment();
+  if (rv != OK) {
+    HistogramCreateSessionFailure(CREATION_ERROR_SETTING_NO_NOT_FRAGMENT);
+    return rv;
+  }
+
   // Set a buffer large enough to contain the initial CWND's worth of packet
   // to work around the problem with CHLO packets being sent out with the
   // wrong encryption level, when the send buffer is full.