[Media Router] Convert MediaRouter to use GURL for presentation URLs.

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 473981c2359bd9502b47eadc5992ca9a1eceecf0..4fa18df1d3fafeddd62e8cee9a1f841a84a74f5a 100644
--- a/content/public/browser/presentation_screen_availability_listener.h
+++ b/content/public/browser/presentation_screen_availability_listener.h
@@ -8,6 +8,7 @@
 #include <string>
 
 #include "content/common/content_export.h"
+#include "url/gurl.h"
 
 namespace content {
 
@@ -21,7 +22,7 @@ class CONTENT_EXPORT PresentationScreenAvailabilityListener {
   // Returns the screen availability URL associated with this listener.
   // Empty string means this object is listening for screen availability
   // for "1-UA" mode, i.e. offscreen tab rendering.
-  virtual std::string GetAvailabilityUrl() const = 0;
+  virtual GURL GetAvailabilityUrl() const = 0;
 
   // Called when screen availability for the associated Presentation URL has
   // changed to |available|.