Handle app custom icon via aura::Window property.

chrome/browser/extensions/chrome_app_icon.cc

 // Copyright 2017 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/extensions/chrome_app_icon.h"
 
 #include <algorithm>
 
 #include "chrome/browser/extensions/chrome_app_icon_delegate.h"
 #include "chrome/browser/extensions/extension_util.h"
@@ skipping 72 matching lines @@
 }
 
 const Extension* ChromeAppIcon::GetExtension() {
   return ExtensionRegistry::Get(browser_context_)
       ->GetInstalledExtension(app_id_);
 }
 
 void ChromeAppIcon::Reload() {
   const Extension* extension = GetExtension();
   icon_ = base::MakeUnique<IconImage>(
-      browser_context_, extension, IconsInfo::GetIcons(extension),
+      browser_context_, extension,
+      extension ? IconsInfo::GetIcons(extension) : ExtensionIconSet(),

[msw, 2017/05/23 00:02:28]

nit: can IconsInfo::GetIcons just return |g_empty_icon_set.Get()| for a null
extension, like it does when the IconsInfo manifest data is null?

[khmel, 2017/05/23 16:11:43]

This might be convenient. Done as recommended.

       resource_size_in_dip_, util::GetDefaultAppIcon(), this);
   UpdateIcon();
 }
 
 bool ChromeAppIcon::IsValid() const {
   DCHECK(icon_);
   return icon_->is_valid();
 }
 
 void ChromeAppIcon::UpdateIcon() {
@@ skipping 18 matching lines @@
 
   delegate_->OnIconUpdated(this);
 }
 
 void ChromeAppIcon::OnExtensionIconImageChanged(IconImage* icon) {
   DCHECK_EQ(icon_.get(), icon);
   UpdateIcon();
 }
 
 }  // namespace extensions