Remove all blimp engine code

blimp/engine/app/ui/blimp_window_tree_host.cc

-// Copyright 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.
-
-#include "blimp/engine/app/ui/blimp_window_tree_host.h"
-
-#include "base/memory/ptr_util.h"
-#include "ui/platform_window/stub/stub_window.h"
-
-namespace blimp {
-namespace engine {
-
-BlimpWindowTreeHost::BlimpWindowTreeHost() : aura::WindowTreeHostPlatform() {
-  CreateCompositor();
-  SetPlatformWindow(base::WrapUnique(new ui::StubWindow(this)));
-}
-
-BlimpWindowTreeHost::~BlimpWindowTreeHost() {}
-
-void BlimpWindowTreeHost::OnAcceleratedWidgetAvailable(
-    gfx::AcceleratedWidget widget,
-    float device_pixel_ratio) {
-  // Do nothing to avoid creating an output surface and gpu process.
-}
-
-}  // namespace engine
-}  // namespace blimp