Make DisplayInfoProvider an interface

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

 // 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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_API_SYSTEM_DISPLAY_DISPLAY_INFO_PROVIDER_H_
 #define CHROME_BROWSER_EXTENSIONS_API_SYSTEM_DISPLAY_DISPLAY_INFO_PROVIDER_H_
 
 #include <string>
 #include <vector>
 

[James Cook, 2014/08/15 19:58:42]

nit: #include "base/macros.h" for DISALLOW_COPY_AND_ASSIGN

 #include "chrome/common/extensions/api/system_display.h"

[James Cook, 2014/08/15 19:58:42]

nit: Can you forward declare api::system_display::DisplayProperties and
DisplayUnitInfo to avoid this include?

 
 namespace gfx {
 class Display;
 }
 
 namespace extensions {
 
 typedef std::vector<linked_ptr<
     api::system_display::DisplayUnitInfo> > DisplayInfo;
 
 class DisplayInfoProvider {
  public :
   static DisplayInfoProvider* Get();
 
-  DisplayInfoProvider();
   virtual ~DisplayInfoProvider();
 
   // This is for tests that run in its own process (e.g. browser_tests).
   // Using this in other tests (e.g. unit_tests) will result in DCHECK failure.
   static void InitializeForTesting(DisplayInfoProvider* display_info_provider);
 
   DisplayInfo GetAllDisplaysInfo();
 
   virtual bool SetInfo(const std::string& display_id,

[James Cook, 2014/08/15 19:58:42]

Please document this method.

                        const api::system_display::DisplayProperties& info,
-                       std::string* error);
+                       std::string* error) = 0;
+
+ protected:
+  DisplayInfoProvider();
 
  private:
   // Update the content of the |unit| obtained for |display| using
   // platform specific method.
   virtual void UpdateDisplayUnitInfoForPlatform(
       const gfx::Display& display,
-      extensions::api::system_display::DisplayUnitInfo* unit);
+      extensions::api::system_display::DisplayUnitInfo* unit) = 0;
 
   DISALLOW_COPY_AND_ASSIGN(DisplayInfoProvider);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_SYSTEM_DISPLAY_DISPLAY_INFO_PROVIDER_H_