reland r57885 with a fix for linux/views.

chrome/browser/gtk/focus_store_gtk.cc

 // Copyright (c) 2010 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/gtk/focus_store_gtk.h"
 
 #include <gtk/gtk.h>
 
 #include "base/logging.h"
 #include "chrome/browser/platform_util.h"
 
 FocusStoreGtk::FocusStoreGtk()
     : widget_(NULL),
       destroy_handler_id_(0) {
 }
 
 FocusStoreGtk::~FocusStoreGtk() {
   DisconnectDestroyHandler();
 }
 
 void FocusStoreGtk::Store(GtkWidget* widget) {
-  DisconnectDestroyHandler();
-  if (!widget) {
-    widget_ = NULL;
-    return;
+  GtkWidget* focus_widget = NULL;
+  if (widget) {
+    GtkWindow* window = platform_util::GetTopLevel(widget);
+    if (window)
+      focus_widget = window->focus_widget;
   }
 
-  GtkWindow* window = platform_util::GetTopLevel(widget);
-  if (!window) {
-    widget_ = NULL;
-    return;
-  }
+  SetWidget(focus_widget);
+}
 
-  widget_ = window->focus_widget;
+void FocusStoreGtk::SetWidget(GtkWidget* widget) {
+  DisconnectDestroyHandler();
+
+  // We don't add a ref. The signal handler below effectively gives us a weak
+  // reference.
+  widget_ = widget;
   if (widget_) {
     // When invoked, |gtk_widget_destroyed| will set |widget_| to NULL.
     destroy_handler_id_ = g_signal_connect(widget_, "destroy",
                                            G_CALLBACK(gtk_widget_destroyed),
                                            &widget_);
   }
 }
 
 void FocusStoreGtk::DisconnectDestroyHandler() {
-  if (widget_)
+  if (widget_) {
     g_signal_handler_disconnect(widget_, destroy_handler_id_);
+    widget_ = NULL;
+  }
 }