Initial gtk3 support

chrome/browser/ui/libgtk2ui/owned_widget_gtk2.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 "chrome/browser/ui/libgtk2ui/owned_widget_gtk2.h"
 
 #include <gtk/gtk.h>
 
 #include "base/logging.h"
 
 namespace libgtk2ui {
 
 OwnedWidgetGtk::~OwnedWidgetGtk() {
   Destroy();
 }
 
 void OwnedWidgetGtk::Own(GtkWidget* widget) {
   if (!widget)
     return;
 
   DCHECK(!widget_);
-  // We want to make sure that Own() was called properly, right after the
-  // widget was created. There should be a floating reference.
-  DCHECK(g_object_is_floating(widget));
 
-  // Sink the floating reference, we should now own this reference.
+  // Keep a reference
   g_object_ref_sink(widget);
   widget_ = widget;
 }
 
 void OwnedWidgetGtk::Destroy() {
   if (!widget_)
     return;
 
   GtkWidget* widget = widget_;
   widget_ = NULL;
   gtk_widget_destroy(widget);
 
   DCHECK(!g_object_is_floating(widget));
   // NOTE: Assumes some implementation details about glib internals.
   DCHECK_EQ(G_OBJECT(widget)->ref_count, 1U);
   g_object_unref(widget);
 }
 
 }  // namespace libgtk2ui