Make DisplayInfoProvider an interface

chrome/browser/extensions/display_info_provider_impl.cc

+// Copyright 2014 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/display_info_provider_impl.h"
+
+namespace extensions {
+
+namespace {
+
+DisplayInfoProvider* g_display_info_provider = NULL;
+
+}  // namespace
+
+// static
+DisplayInfoProvider* DisplayInfoProvider::Get() {
+  if (g_display_info_provider == NULL)
+    g_display_info_provider = new DisplayInfoProviderImpl();
+  return g_display_info_provider;
+}
+
+// static
+void DisplayInfoProvider::InitializeForTesting(
+    DisplayInfoProvider* display_info_provider) {
+  DCHECK(display_info_provider);
+  g_display_info_provider = display_info_provider;
+}
+
+DisplayInfoProviderImpl::DisplayInfoProviderImpl() {}
+
+DisplayInfoProviderImpl::~DisplayInfoProviderImpl() {}
+
+}  // namespace extensions