Fix prefs migration for font settings.

chrome/browser/ui/prefs/prefs_tab_helper.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/prefs/prefs_tab_helper.h"
 
 #include "base/string_util.h"
 #include "base/stringprintf.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/browser/browser_process.h"
@@ skipping 305 matching lines @@
 
 static void MigratePreferences(PrefService* prefs) {
   RegisterFontsAndCharsetPrefs(prefs);
   for (int i = 0; i < kPrefsToMigrateLength; ++i) {
     const PrefService::Preference *pref =
         prefs->FindPreference(kPrefNamesToMigrate[i].from);
     if (!pref) continue;
     if (!pref->IsDefaultValue()) {
       prefs->Set(kPrefNamesToMigrate[i].to, *pref->GetValue()->DeepCopy());
     }
+    prefs->ClearPref(kPrefNamesToMigrate[i].from);
     prefs->UnregisterPreference(kPrefNamesToMigrate[i].from);
   }
 }
 
 }  // namespace
 
 PrefsTabHelper::PrefsTabHelper(WebContents* contents)
     : content::WebContentsObserver(contents) {
   PrefService* prefs = GetProfile()->GetPrefs();
   pref_change_registrar_.Init(prefs);
@@ skipping 322 matching lines @@
 
 void PrefsTabHelper::UpdateRendererPreferences() {
   renderer_preferences_util::UpdateFromSystemSettings(
       web_contents()->GetMutableRendererPrefs(), GetProfile());
   web_contents()->GetRenderViewHost()->SyncRendererPrefs();
 }
 
 Profile* PrefsTabHelper::GetProfile() {
   return Profile::FromBrowserContext(web_contents()->GetBrowserContext());
 }