Get rid of PrefService::GetMutableDictionary/GetMutableList

chrome/browser/ui/gtk/task_manager_gtk.cc

Index: chrome/browser/ui/gtk/task_manager_gtk.cc
diff --git a/chrome/browser/ui/gtk/task_manager_gtk.cc b/chrome/browser/ui/gtk/task_manager_gtk.cc
index d1371220867f70bf4547e9bf3d769f4ea6e95fd1..b5d4ecfbf9d57ba368bc82fe345be709b450700e 100644
--- a/chrome/browser/ui/gtk/task_manager_gtk.cc
+++ b/chrome/browser/ui/gtk/task_manager_gtk.cc
@@ -19,6 +19,7 @@
 #include "chrome/browser/defaults.h"
 #include "chrome/browser/memory_purger.h"
 #include "chrome/browser/prefs/pref_service.h"
+#include "chrome/browser/prefs/scoped_user_pref_update.h"
 #include "chrome/browser/ui/gtk/gtk_chrome_link_button.h"
 #include "chrome/browser/ui/gtk/gtk_theme_service.h"
 #include "chrome/browser/ui/gtk/gtk_tree.h"
@@ -863,9 +864,9 @@ void TaskManagerGtk::OnResponse(GtkWidget* dialog, int response_id) {
     if (g_browser_process->local_state()) {
       gfx::Rect dialog_bounds = gtk_util::GetDialogBounds(GTK_WIDGET(dialog));
 
-      DictionaryValue* placement_pref =
-          g_browser_process->local_state()->GetMutableDictionary(
-              prefs::kTaskManagerWindowPlacement);
+      DictionaryPrefUpdate update(g_browser_process->local_state(),
+                                  prefs::kTaskManagerWindowPlacement);
+      DictionaryValue* placement_pref = update.Get();
       // Note that we store left/top for consistency with Windows, but that we
       // *don't* restore them.
       placement_pref->SetInteger("left", dialog_bounds.x());