Set the WM_CLASS property of X11 windows in Linux Aura build.

ui/views/widget/widget.h

Index: ui/views/widget/widget.h
diff --git a/ui/views/widget/widget.h b/ui/views/widget/widget.h
index e6067eba1e80e9c86a0346180eda7ff885029611..0dca9ec34fce74ee0e78449dbc65417b6b176c11 100644
--- a/ui/views/widget/widget.h
+++ b/ui/views/widget/widget.h
@@ -216,6 +216,11 @@ class VIEWS_EXPORT Widget : public internal::NativeWidgetDelegate,
     // where it wants your window placed.) NULL is not allowed if you are using
     // aura.
     gfx::NativeView context;
+    // Only used by X11, for root level windows. Specifies the res_name and
+    // res_class fields, respectively, of the WM_CLASS window property. Controls
+    // window grouping and desktop file matching in Linux window managers.
+    std::string wm_class_name;
+    std::string wm_class_class;
   };
 
   Widget();