Gtk3 ui: Add libgtk3ui as a separate build component

chrome/browser/ui/libgtkui/x11_input_method_context_impl_gtk2.cc

 // Copyright 2013 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/x11_input_method_context_impl_gtk2.h"
+#include "chrome/browser/ui/libgtkui/x11_input_method_context_impl_gtk2.h"
 
 #include <gdk/gdk.h>
 #include <gdk/gdkkeysyms.h>
 #include <gdk/gdkx.h>
 #include <stddef.h>
 
 #include <gtk/gtk.h>
 
 #include <X11/X.h>
 #include <X11/Xlib.h>
 
 #include "base/message_loop/message_loop.h"
 #include "base/strings/utf_string_conversions.h"
 #include "ui/base/ime/composition_text.h"
 #include "ui/base/ime/composition_text_util_pango.h"
 #include "ui/base/ime/text_input_client.h"
 #include "ui/events/event.h"
 #include "ui/events/keycodes/keyboard_code_conversion_x.h"
 #include "ui/gfx/x/x11_types.h"
 
-namespace libgtk2ui {
+namespace libgtkui {
 
 X11InputMethodContextImplGtk2::X11InputMethodContextImplGtk2(
     ui::LinuxInputMethodContextDelegate* delegate,
     bool is_simple)
     : delegate_(delegate),
       gtk_context_(NULL),
       gdk_last_set_client_window_(NULL) {
   CHECK(delegate_);
 
   ResetXModifierKeycodesCache();
@@ skipping 269 matching lines @@
   delegate_->OnPreeditEnd();
 }
 
 void X11InputMethodContextImplGtk2::OnPreeditStart(GtkIMContext* context) {
   if (context != gtk_context_)
     return;
 
   delegate_->OnPreeditStart();
 }
 
-}  // namespace libgtk2ui
+}  // namespace libgtkui