Revert of Fix crash when user closes window prior to the "Confirm Install" prompt showing

chrome/browser/ui/native_window_tracker.h

Index: chrome/browser/ui/native_window_tracker.h
diff --git a/chrome/browser/ui/native_window_tracker.h b/chrome/browser/ui/native_window_tracker.h
deleted file mode 100644
index c08dc126546b766861acc8cecc5d0097a5f93d28..0000000000000000000000000000000000000000
--- a/chrome/browser/ui/native_window_tracker.h
+++ /dev/null
@@ -1,22 +0,0 @@
-// Copyright 2014 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 CHROME_BROWSER_UI_NATIVE_WINDOW_TRACKER_H_
-#define CHROME_BROWSER_UI_NATIVE_WINDOW_TRACKER_H_
-
-#include "base/memory/scoped_ptr.h"
-#include "ui/gfx/native_widget_types.h"
-
-// An observer which detects when a gfx::NativeWindow is closed.
-class NativeWindowTracker {
- public:
-  virtual ~NativeWindowTracker() {}
-
-  static scoped_ptr<NativeWindowTracker> Create(gfx::NativeWindow window);
-
-  // Returns true if the native window passed to Create() has been closed.
-  virtual bool WasNativeWindowClosed() const = 0;
-};
-
-#endif  // CHROME_BROWSER_UI_NATIVE_WINDOW_TRACKER_H_