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

chrome/browser/ui/native_window_deletion_observer.h

Index: chrome/browser/ui/native_window_deletion_observer.h
diff --git a/chrome/browser/ui/native_window_deletion_observer.h b/chrome/browser/ui/native_window_deletion_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..4b37e464ccbe87694214c9e658d29f5976a291d8
--- /dev/null
+++ b/chrome/browser/ui/native_window_deletion_observer.h
@@ -0,0 +1,23 @@
+// 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_DELETION_OBSERVER_H_
+#define CHROME_BROWSER_UI_NATIVE_WINDOW_DELETION_OBSERVER_H_
+
+#include "base/memory/scoped_ptr.h"
+#include "ui/gfx/native_widget_types.h"
+
+// An observer which can be probed for the life of a gfx::NativeWindow.
+class NativeWindowDeletionObserver {

[sky, 2014/10/24 20:22:56]

I would be inclined to name this NativeWindowTracker (similar to
ui/aura/window_tracker). But I don't feel strongly. If you prefer this name, go
with it.

+ public:
+  static scoped_ptr<NativeWindowDeletionObserver> Create(

[sky, 2014/10/24 20:22:56]

style guide says constructor/destructor before other functions (including
static).

+      gfx::NativeWindow window);
+
+  virtual ~NativeWindowDeletionObserver() {}
+
+  // Returns true if the native window passed to Create() is still alive.
+  virtual bool IsNativeWindowAlive() const = 0;
+};
+
+#endif  // CHROME_BROWSER_UI_NATIVE_WINDOW_DELETION_OBSERVER_H_