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

net/tools/quic/test_tools/limited_mtu_test_writer.h

Index: net/tools/quic/test_tools/limited_mtu_test_writer.h
diff --git a/net/tools/quic/test_tools/limited_mtu_test_writer.h b/net/tools/quic/test_tools/limited_mtu_test_writer.h
new file mode 100644
index 0000000000000000000000000000000000000000..f3021651bc10f9613cda224dee597bdcb1ecb3a0
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+++ b/net/tools/quic/test_tools/limited_mtu_test_writer.h
@@ -0,0 +1,39 @@
+// Copyright (c) 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef NET_TOOLS_QUIC_TEST_TOOLS_LIMITED_MTU_TEST_WRITER_H_
+#define NET_TOOLS_QUIC_TEST_TOOLS_LIMITED_MTU_TEST_WRITER_H_
+
+#include "base/basictypes.h"
+#include "net/quic/quic_protocol.h"
+#include "net/tools/quic/quic_packet_writer_wrapper.h"
+
+namespace net {
+namespace tools {
+namespace test {
+
+// Simulates a connection over a link with fixed MTU.  Drops packets which
+// exceed the MTU and passes the rest of them as-is.
+class LimitedMtuTestWriter : public QuicPacketWriterWrapper {
+ public:
+  explicit LimitedMtuTestWriter(QuicByteCount mtu);
+  ~LimitedMtuTestWriter() override;
+
+  // Inherited from QuicPacketWriterWrapper.
+  WriteResult WritePacket(const char* buffer,
+                          size_t buf_len,
+                          const IPAddressNumber& self_address,
+                          const IPEndPoint& peer_address) override;
+
+ private:
+  QuicByteCount mtu_;
+
+  DISALLOW_COPY_AND_ASSIGN(LimitedMtuTestWriter);
+};
+
+}  // namespace test
+}  // namespace tools
+}  // namespace net
+
+#endif  // NET_TOOLS_QUIC_TEST_TOOLS_LIMITED_MTU_TEST_WRITER_H_