Small fix for PresentationScreenAvailabilityListener.

content/public/browser/presentation_screen_availability_listener.h

Index: content/public/browser/presentation_screen_availability_listener.h
diff --git a/content/public/browser/presentation_screen_availability_listener.h b/content/public/browser/presentation_screen_availability_listener.h
index 4ed8749bcfe4f49b04b17b87a187d504fcfe3ec9..111484762fc852fc722ce97f7415400ed759df94 100644
--- a/content/public/browser/presentation_screen_availability_listener.h
+++ b/content/public/browser/presentation_screen_availability_listener.h
@@ -14,15 +14,14 @@ namespace content {
 // See also PresentationServiceDelegate.
 class PresentationScreenAvailabilityListener {
  public:
+  virtual ~PresentationScreenAvailabilityListener() {}
+
   // Returns the Presentation URL associated with this listener.
-  virtual std::string GetPresentationUrl() = 0;
+  virtual std::string GetPresentationUrl() const = 0;
 
   // Called when screen availability for the associated Presentation URL has
   // changed to |available|.
   virtual void OnScreenAvailabilityChanged(bool available) = 0;
-
- protected:
-  virtual ~ScreenAvailabilityListener() {}
 };
 
 }  // namespace content