Move session into //blimp/client/app and update GN files.

blimp/client/session/test_client_session.cc

Index: blimp/client/session/test_client_session.cc
diff --git a/blimp/client/session/test_client_session.cc b/blimp/client/session/test_client_session.cc
deleted file mode 100644
index cf25a455ca8aa56b7366f7d151f8b6adbba75c64..0000000000000000000000000000000000000000
--- a/blimp/client/session/test_client_session.cc
+++ /dev/null
@@ -1,20 +0,0 @@
-// Copyright 2016 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.
-
-#include "blimp/client/session/test_client_session.h"
-
-namespace blimp {
-namespace client {
-namespace {
-// Assigner is not actually used in this test.
-const char kAssignerUrl[] = "http://www.assigner.test/";
-}  // namespace
-
-TestClientSession::TestClientSession()
-    : client::BlimpClientSession(GURL(kAssignerUrl)) {}
-
-TestClientSession::~TestClientSession() {}
-
-}  // namespace client
-}  // namespace blimp