Revert of Add ExtensionsApiClient interface, use it in the storage API SettingsFrontend

extensions/browser/api/storage/settings_namespace.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 "extensions/browser/api/storage/settings_namespace.h"
-
-#include "base/logging.h"
-
-namespace extensions {
-
-namespace settings_namespace {
-
-namespace {
-const char kLocalNamespace[] = "local";
-const char kSyncNamespace[] = "sync";
-const char kManagedNamespace[] = "managed";
-}  // namespace
-
-std::string ToString(Namespace settings_namespace) {
-  switch (settings_namespace) {
-    case LOCAL:
-      return kLocalNamespace;
-    case SYNC:
-      return kSyncNamespace;
-    case MANAGED:
-      return kManagedNamespace;
-    case INVALID:
-      break;
-  }
-  NOTREACHED();
-  return std::string();
-}
-
-Namespace FromString(const std::string& namespace_string) {
-  if (namespace_string == kLocalNamespace)
-    return LOCAL;
-  if (namespace_string == kSyncNamespace)
-    return SYNC;
-  if (namespace_string == kManagedNamespace)
-    return MANAGED;
-  return INVALID;
-}
-
-}  // namespace settings_namespace
-
-}  // namespace extensions