views: Packaged app window icon should be system/generic icon, if icon is not set by default.

ui/views/win/hwnd_message_handler.h

Index: ui/views/win/hwnd_message_handler.h
diff --git a/ui/views/win/hwnd_message_handler.h b/ui/views/win/hwnd_message_handler.h
index 73d6c3e228c712e5e2a982b048acab4f2ea2ee60..2c32328c6bdb1dab2ec29a99991521d6cb77d5bc 100644
--- a/ui/views/win/hwnd_message_handler.h
+++ b/ui/views/win/hwnd_message_handler.h
@@ -150,6 +150,10 @@ class VIEWS_EXPORT HWNDMessageHandler : public ui::WindowImpl,
     remove_standard_frame_ = remove_standard_frame;
   }
 
+  void set_use_system_default_icon(bool use_system_default_icon) {
+    use_sytem_default_icon_ = use_system_default_icon;
+  }
+
  private:
   typedef std::set<DWORD> TouchIDs;
 
@@ -367,6 +371,8 @@ class VIEWS_EXPORT HWNDMessageHandler : public ui::WindowImpl,
 
   bool remove_standard_frame_;
 
+  bool use_sytem_default_icon_;
+
   // Whether the focus should be restored next time we get enabled.  Needed to
   // restore focus correctly when Windows modal dialogs are displayed.
   bool restore_focus_when_enabled_;