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

chrome/browser/ui/cocoa/native_window_tracker_cocoa.mm

-// 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.
-
-#include "chrome/browser/ui/cocoa/native_window_tracker_cocoa.h"
-
-#import <AppKit/AppKit.h>
-
-@interface BridgedNativeWindowTracker : NSObject {
- @private
-  NSWindow* window_;
-}
-
-- (id)initWithNSWindow:(NSWindow*)window;
-- (bool)wasNSWindowClosed;
-- (void)onWindowWillClose:(NSNotification*)notification;
-
-@end
-
-@implementation BridgedNativeWindowTracker
-
-- (id)initWithNSWindow:(NSWindow*)window {
-  window_ = window;
-  NSNotificationCenter* center = [NSNotificationCenter defaultCenter];
-  [center addObserver:self
-             selector:@selector(onWindowWillClose:)
-                 name:NSWindowWillCloseNotification
-               object:window_];
-  return self;
-}
-
-- (void)dealloc {
-  [[NSNotificationCenter defaultCenter] removeObserver:self];
-  [super dealloc];
-}
-
-- (bool)wasNSWindowClosed {
-  return window_ == nil;
-}
-
-- (void)onWindowWillClose:(NSNotification*)notification {
-  [[NSNotificationCenter defaultCenter]
-      removeObserver:self
-                name:NSWindowWillCloseNotification
-              object:window_];
-  window_ = nil;
-}
-
-@end
-
-NativeWindowTrackerCocoa::NativeWindowTrackerCocoa(gfx::NativeWindow window) {
-  bridge_.reset([[BridgedNativeWindowTracker alloc] initWithNSWindow:window]);
-}
-
-NativeWindowTrackerCocoa::~NativeWindowTrackerCocoa() {
-}
-
-bool NativeWindowTrackerCocoa::WasNativeWindowClosed() const {
-  return [bridge_ wasNSWindowClosed];
-}
-
-// static
-scoped_ptr<NativeWindowTracker> NativeWindowTracker::Create(
-    gfx::NativeWindow window) {
-  return scoped_ptr<NativeWindowTracker>(new NativeWindowTrackerCocoa(window));
-}