Add quic_test_loopback used for tests only.

net/BUILD.gn

 # Copyright (c) 2013 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.
 
 import("//build/buildflag_header.gni")
 import("//build/config/chromecast_build.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
@@ skipping 3021 matching lines @@
       "//build/config:exe_and_shlib_deps",
     ]
   }
 }
 
 source_set("quic_test_tools") {
   testonly = true
   sources = [
     "quic/chromium/crypto_test_utils_chromium.cc",
     "quic/platform/api/quic_test.h",
+    "quic/platform/api/quic_test_loopback.cc",
+    "quic/platform/api/quic_test_loopback.h",
     "quic/platform/impl/quic_test_impl.cc",
     "quic/platform/impl/quic_test_impl.h",
+    "quic/platform/impl/quic_test_loopback_impl.cc",
+    "quic/platform/impl/quic_test_loopback_impl.h",
     "quic/test_tools/crypto_test_utils.cc",
     "quic/test_tools/crypto_test_utils.h",
     "quic/test_tools/delayed_verify_strike_register_client.cc",
     "quic/test_tools/delayed_verify_strike_register_client.h",
     "quic/test_tools/failing_proof_source.cc",
     "quic/test_tools/failing_proof_source.h",
     "quic/test_tools/fake_proof_source.cc",
     "quic/test_tools/fake_proof_source.h",
     "quic/test_tools/mock_clock.cc",
     "quic/test_tools/mock_clock.h",
@@ skipping 3004 matching lines @@
   ]
   deps = [
     ":net_fuzzer_test_support",
     ":test_support",
     "//base",
     "//net",
   ]
   dict = "data/fuzzer_dictionaries/net_spdy_session_fuzzer.dict"
   seed_corpus = "data/fuzzer_data/net_spdy_session_fuzzer/"
 }