Allow QuicClient to set connection MTU before the handshake is sent.

net/tools/quic/quic_simple_client.h

Index: net/tools/quic/quic_simple_client.h
diff --git a/net/tools/quic/quic_simple_client.h b/net/tools/quic/quic_simple_client.h
index cb709709fb76d87357d31c25d8421772fa774f1b..dcedb1ab676a4cbb3fdc58e8ef9ff1ce43e89c79 100644
--- a/net/tools/quic/quic_simple_client.h
+++ b/net/tools/quic/quic_simple_client.h
@@ -184,6 +184,12 @@ class QuicSimpleClient : public QuicDataStream::Visitor,
   const std::string& latest_response_headers() const;
   const std::string& latest_response_body() const;
 
+  // Change the initial maximum packet size of the connection.  Has to be called
+  // before Connect()/StartConnect() in order to have any effect.
+  void set_initial_max_packet_length(QuicByteCount initial_max_packet_length) {
+    initial_max_packet_length_ = initial_max_packet_length;
+  }
+
  protected:
   virtual QuicConnectionId GenerateConnectionId();
   virtual QuicConnectionHelper* CreateQuicConnectionHelper();
@@ -285,6 +291,10 @@ class QuicSimpleClient : public QuicDataStream::Visitor,
   // Body of most recent response.
   std::string latest_response_body_;
 
+  // The initial value of maximum packet size of the connection.  If set to
+  // zero, the default is used.
+  QuicByteCount initial_max_packet_length_;
+
   // The log used for the sockets.
   NetLog net_log_;