Use Ash's ShelfWindowWatcher for app panel windows.

ui/views/widget/native_widget_aura.cc

Index: ui/views/widget/native_widget_aura.cc
diff --git a/ui/views/widget/native_widget_aura.cc b/ui/views/widget/native_widget_aura.cc
index 345ec9c431285011a9826b41163c27d7e90bffcc..24288c8fe5d137072d4abc5acf72f9af81670f41 100644
--- a/ui/views/widget/native_widget_aura.cc
+++ b/ui/views/widget/native_widget_aura.cc
@@ -74,6 +74,15 @@ void SetRestoreBounds(aura::Window* window, const gfx::Rect& bounds) {
   window->SetProperty(aura::client::kRestoreBoundsKey, new gfx::Rect(bounds));
 }
 
+void SetIcon(aura::Window* window,
+             const aura::WindowProperty<gfx::ImageSkia*>* key,
+             const gfx::ImageSkia& value) {
+  if (value.isNull())
+    window->ClearProperty(key);
+  else
+    window->SetProperty(key, new gfx::ImageSkia(value));
+}
+
 }  // namespace
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -102,17 +111,10 @@ void NativeWidgetAura::RegisterNativeWidgetForWindow(
 void NativeWidgetAura::AssignIconToAuraWindow(aura::Window* window,
                                               const gfx::ImageSkia& window_icon,
                                               const gfx::ImageSkia& app_icon) {
-  if (!window)
-    return;
-
-  if (window_icon.isNull() && app_icon.isNull()) {
-    window->ClearProperty(aura::client::kWindowIconKey);
-    return;
+  if (window) {
+    SetIcon(window, aura::client::kWindowIconKey, window_icon);
+    SetIcon(window, aura::client::kAppIconKey, app_icon);
   }
-
-  window->SetProperty(
-      aura::client::kWindowIconKey,
-      new gfx::ImageSkia(!window_icon.isNull() ? window_icon : app_icon));
 }
 
 ////////////////////////////////////////////////////////////////////////////////