Introduce //components/user_prefs, use to eliminate c/b/prefs dependency in Autofill.

components/user_prefs/user_prefs.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 "components/user_prefs/user_prefs.h"
+
+#include "base/logging.h"
+#include "base/memory/singleton.h"
+
+namespace components {
+
+UserPrefs::UserPrefs() {
+}
+
+UserPrefs::~UserPrefs() {
+}
+
+// static
+UserPrefs* UserPrefs::GetInstance() {
+  return Singleton<UserPrefs>::get();
+}
+
+// static
+PrefService* UserPrefs::Get(content::BrowserContext* context) {
+  return GetInstance()->Lookup(context);
+}
+
+bool UserPrefs::IsInitialized() const {
+  return delegate_.get() != NULL;
+}
+
+void UserPrefs::Initialize(scoped_ptr<UserPrefsDelegate> delegate) {
+  DCHECK(!delegate_.get());
+  delegate_ = delegate.Pass();
+}
+
+PrefService* UserPrefs::Lookup(content::BrowserContext* context) {
+  return delegate_->PrefServiceFromBrowserContext(context);
+}
+
+}  // namespace components