Gtk3 ui: Add libgtk3ui as a separate build component

chrome/browser/ui/libgtkui/gtk2_event_loop.cc

 // Copyright 2014 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/ui/libgtk2ui/gtk2_event_loop.h"
+#include "chrome/browser/ui/libgtkui/gtk2_event_loop.h"
 
 #include <gdk/gdk.h>
 #include <gdk/gdkx.h>
 #include <gtk/gtk.h>
 #include <X11/X.h>
 
 #include "base/memory/singleton.h"
 #include "ui/events/platform/x11/x11_event_source.h"
 #include "ui/gfx/x/x11_types.h"
 
-namespace libgtk2ui {
+namespace libgtkui {
 
 // static
 Gtk2EventLoop* Gtk2EventLoop::GetInstance() {
   return base::Singleton<Gtk2EventLoop>::get();
 }
 
 Gtk2EventLoop::Gtk2EventLoop() {
   gdk_event_handler_set(DispatchGdkEvent, NULL, NULL);
 }
 
@@ skipping 45 matching lines @@
   x_event.xkey.same_screen = true;
 
   // We want to process the gtk2 event; mapped to an X11 event immediately
   // otherwise if we put it back on the queue we may get items out of order.
   if (ui::X11EventSource* x11_source = ui::X11EventSource::GetInstance())
     x11_source->DispatchXEventNow(&x_event);
   else
     XPutBackEvent(x_event.xkey.display, &x_event);
 }
 
-}  // namespace libgtk2ui
+}  // namespace libgtkui