Remove all blimp engine code

blimp/engine/app/test_content_main_delegate.cc

-// 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/engine/app/test_content_main_delegate.h"
-
-namespace blimp {
-namespace engine {
-namespace {
-TestContentMainDelegate* g_content_main_delegate = nullptr;
-}  // namespace
-
-TestContentMainDelegate::TestContentMainDelegate() {
-  DCHECK(!g_content_main_delegate);
-  g_content_main_delegate = this;
-}
-
-TestContentMainDelegate::~TestContentMainDelegate() {
-  DCHECK_EQ(this, g_content_main_delegate);
-  g_content_main_delegate = nullptr;
-}
-
-// static
-TestContentMainDelegate* TestContentMainDelegate::GetInstance() {
-  return g_content_main_delegate;
-}
-
-}  // namespace engine
-}  // namespace blimp