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

chrome/browser/ui/aura/native_window_deletion_observer_aura.cc

Index: chrome/browser/ui/aura/native_window_deletion_observer_aura.cc
diff --git a/chrome/browser/ui/aura/native_window_deletion_observer_aura.cc b/chrome/browser/ui/aura/native_window_deletion_observer_aura.cc
new file mode 100644
index 0000000000000000000000000000000000000000..e0dbde2374046b87e7814d086b4d871165d82304
--- /dev/null
+++ b/chrome/browser/ui/aura/native_window_deletion_observer_aura.cc
@@ -0,0 +1,35 @@
+// 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/aura/native_window_deletion_observer_aura.h"
+
+#include "ui/aura/window.h"
+
+NativeWindowDeletionObserverAura::NativeWindowDeletionObserverAura(
+    gfx::NativeWindow window)
+  : window_(window) {

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

nit: indent 2 more.

+  window->AddObserver(this);
+}
+
+NativeWindowDeletionObserverAura::~NativeWindowDeletionObserverAura() {
+  if (window_)
+    window_->RemoveObserver(this);
+}
+
+bool NativeWindowDeletionObserverAura::IsNativeWindowAlive() const {
+  return window_;

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

I'm surprised the compiler is happy with this. Usually you need the != nullptr,
or !!.

+}
+
+void NativeWindowDeletionObserverAura::OnWindowDestroying(
+    aura::Window* window) {
+  window_->RemoveObserver(this);
+  window_ = NULL;

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

nullptr.

+}
+
+// static
+scoped_ptr<NativeWindowDeletionObserver> NativeWindowDeletionObserver::Create(
+    gfx::NativeWindow window) {
+  return scoped_ptr<NativeWindowDeletionObserver>(
+      new NativeWindowDeletionObserverAura(window));
+}