set WM_CLASS in X11 window host.

ui/aura/window_tree_host_x11.cc

Index: ui/aura/window_tree_host_x11.cc
diff --git a/ui/aura/window_tree_host_x11.cc b/ui/aura/window_tree_host_x11.cc
index 37efdf4b65b98773ed5e6c2d276d375c6a7f76bc..a9a23d441163d9e057d9f189e2152e949fb5feb7 100644
--- a/ui/aura/window_tree_host_x11.cc
+++ b/ui/aura/window_tree_host_x11.cc
@@ -157,9 +157,14 @@ WindowTreeHostX11::WindowTreeHostX11(const gfx::Rect& bounds)
   protocols[1] = atom_cache_.GetAtom("_NET_WM_PING");
   XSetWMProtocols(xdisplay_, xwindow_, protocols, 2);
 
+  XClassHint* class_hint = XAllocClassHint();
+  class_hint->res_name = const_cast<char*>("chromiumos");
+  class_hint->res_class = const_cast<char*>("ChromiumOS");
   // We need a WM_CLIENT_MACHINE and WM_LOCALE_NAME value so we integrate with
   // the desktop environment.
-  XSetWMProperties(xdisplay_, xwindow_, NULL, NULL, NULL, 0, NULL, NULL, NULL);
+  XSetWMProperties(xdisplay_, xwindow_, NULL, NULL, NULL, 0, NULL, NULL,
+                   class_hint);
+  XFree(class_hint);

[sadrul, 2016/11/16 00:29:44]

Can you use ui::SetWindowClassHint() instead?

[Muyuan, 2016/11/16 00:51:43]

Done.

 
   // Likewise, the X server needs to know this window's pid so it knows which
   // program to kill if the window hangs.