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

net/tools/quic/quic_client.h

Index: net/tools/quic/quic_client.h
diff --git a/net/tools/quic/quic_client.h b/net/tools/quic/quic_client.h
index 609ad44b8eccaf00e157861ce9cebe852b3cd578..3a35b6d5a4992d5527a383b11167c0f84ff1aea5 100644
--- a/net/tools/quic/quic_client.h
+++ b/net/tools/quic/quic_client.h
@@ -201,6 +201,12 @@ class QuicClient : public EpollCallbackInterface,
   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 QuicEpollConnectionHelper* CreateQuicConnectionHelper();
@@ -298,6 +304,10 @@ class QuicClient : public EpollCallbackInterface,
   // 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_;
+
   DISALLOW_COPY_AND_ASSIGN(QuicClient);
 };