Nukes aura::WindowDestructionObserver. It's effectively the same as

content/browser/renderer_host/render_widget_host_view_aura.cc

Index: content/browser/renderer_host/render_widget_host_view_aura.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.cc b/content/browser/renderer_host/render_widget_host_view_aura.cc
index dc239349e4d65a872c5b0bee4f1603740e051823..15baa0a54085bb5a235e9c295a9ff0ef315a3e34 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura.cc
@@ -54,7 +54,6 @@
 #include "ui/aura/env.h"
 #include "ui/aura/root_window.h"
 #include "ui/aura/window.h"
-#include "ui/aura/window_destruction_observer.h"
 #include "ui/aura/window_observer.h"
 #include "ui/aura/window_tracker.h"
 #include "ui/base/clipboard/scoped_clipboard_writer.h"
@@ -2476,12 +2475,13 @@ void RenderWidgetHostViewAura::OnKeyEvent(ui::KeyEvent* event) {
       aura::Window* host = *(host_tracker_->windows().begin());
       aura::client::FocusClient* client = aura::client::GetFocusClient(host);
       if (client) {
-        // Calling host->Focus() may delete |this|. We create a local
-        // observer for that. In that case we exit without further
-        // access to any members.
-        aura::WindowDestructionObserver destruction_observer(window_);
+        // Calling host->Focus() may delete |this|. We create a local observer
+        // for that. In that case we exit without further access to any members.
+        aura::WindowTracker tracker;
+        aura::Window* window = window_;
+        tracker.Add(window);
         host->Focus();
-        if (destruction_observer.destroyed()) {
+        if (!tracker.Contains(window)) {
           event->SetHandled();
           return;
         }