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

chrome/browser/extensions/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 "chrome/browser/extensions/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