set WM_CLASS in X11 window host.

ui/aura/window_tree_host_x11.cc

 // Copyright (c) 2012 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 "ui/aura/window_tree_host_x11.h"
 
 #include <strings.h>
 #include <X11/cursorfont.h>
 #include <X11/extensions/XInput2.h>
 #include <X11/extensions/Xrandr.h>
@@ skipping 139 matching lines @@
   }
 
   // TODO(erg): We currently only request window deletion events. We also
   // should listen for activation events and anything else that GTK+ listens
   // for, and do something useful.
   ::Atom protocols[2];
   protocols[0] = atom_cache_.GetAtom("WM_DELETE_WINDOW");
   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.
   // XChangeProperty() expects "pid" to be long.
   static_assert(sizeof(long) >= sizeof(pid_t),
                 "pid_t should not be larger than long");
   long pid = getpid();
   XChangeProperty(xdisplay_,
                   xwindow_,
                   atom_cache_.GetAtom("_NET_WM_PID"),
@@ skipping 401 matching lines @@
 }
 
 namespace test {
 
 void SetUseOverrideRedirectWindowByDefault(bool override_redirect) {
   default_override_redirect = override_redirect;
 }
 
 }  // namespace test
 }  // namespace aura