Make DisplayInfoProvider an interface

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

Index: chrome/browser/extensions/api/system_display/display_info_provider.h
diff --git a/chrome/browser/extensions/api/system_display/display_info_provider.h b/chrome/browser/extensions/api/system_display/display_info_provider.h
index 50eec2e0d1484401959ee65922f0fbdbbac4f27c..13995606000a7bdfac067bc2f4f44cbc71b539fe 100644
--- a/chrome/browser/extensions/api/system_display/display_info_provider.h
+++ b/chrome/browser/extensions/api/system_display/display_info_provider.h
@@ -23,7 +23,6 @@ class DisplayInfoProvider {
  public :
   static DisplayInfoProvider* Get();
 
-  DisplayInfoProvider();
   virtual ~DisplayInfoProvider();
 
   // This is for tests that run in its own process (e.g. browser_tests).
@@ -34,14 +33,17 @@ class DisplayInfoProvider {
 
   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);
 };