Add additional properties to display system info on ChromeOS

chrome/browser/extensions/api/system_info_display/display_info_provider.h

 // 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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_API_SYSTEM_INFO_DISPLAY_DISPLAY_INFO_PROVIDER_H_
 #define CHROME_BROWSER_EXTENSIONS_API_SYSTEM_INFO_DISPLAY_DISPLAY_INFO_PROVIDER_H_
 
 #include "chrome/browser/extensions/api/system_info/system_info_provider.h"
 #include "chrome/common/extensions/api/system_info_display.h"
 
 namespace extensions {
 
 typedef std::vector<linked_ptr<
     api::system_info_display::DisplayUnitInfo> > DisplayInfo;
 
 class DisplayInfoProvider : public SystemInfoProvider<DisplayInfo> {
  public:
-  static DisplayInfoProvider* GetDisplayInfo();
+  typedef base::Callback<void(const DisplayInfo& info, bool success)>
+      RequestInfoCallback;
 
+  // Gets a DisplayInfoProvider instance.
+  static DisplayInfoProvider* GetProvider();
+
+  // Starts request for the display info, redirecting the request to a worker
+  // thread if needed (using SystemInfoProvider<DisplayInfo>::StartQuery()).
+  // The callback will be called asynchronously.
+  // The implementation is platform specific.
+  void RequestInfo(const RequestInfoCallback& callback);
+
+ protected:
   // Overriden from SystemInfoProvider<DisplayInfo>.
+  // The implementation is platform specific.
   virtual bool QueryInfo(DisplayInfo* info) OVERRIDE;
 
- protected:
   friend class SystemInfoProvider<DisplayInfo>;
 
   DisplayInfoProvider() {}
   virtual ~DisplayInfoProvider() {}
 
   DISALLOW_COPY_AND_ASSIGN(DisplayInfoProvider);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_SYSTEM_INFO_DISPLAY_DISPLAY_INFO_PROVIDER_H_