Make DisplayInfoProvider an interface

chrome/browser/extensions/display_info_provider_mac.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 "chrome/browser/extensions/api/system_display/display_info_provider.h"
+#include "chrome/browser/extensions/display_info_provider_mac.h"
 
 namespace extensions {
 
-bool DisplayInfoProvider::SetInfo(const std::string& display_id,
+DisplayInfoProviderMac::DisplayInfoProviderMac() {
+}
+
+DisplayInfoProviderMac::~DisplayInfoProviderMac() {
+}
+
+bool DisplayInfoProviderMac::SetInfo(
+    const std::string& display_id,
     const api::system_display::DisplayProperties& info,
     std::string* error) {
-  *error = "Not Implemented";
+  *error = "Not implemented";
   return false;
 }
 
-void DisplayInfoProvider::UpdateDisplayUnitInfoForPlatform(
+void DisplayInfoProviderMac::UpdateDisplayUnitInfoForPlatform(
     const gfx::Display& display,
     extensions::api::system_display::DisplayUnitInfo* unit) {
   NOTIMPLEMENTED();
 }
 
+// static
+DisplayInfoProvider* DisplayInfoProvider::Create() {
+  return new DisplayInfoProviderMac();
+}
+
 }  // namespace extensions