Add IsInternal property to gfx::Display

ash/display/display_manager.h

Index: ash/display/display_manager.h
diff --git a/ash/display/display_manager.h b/ash/display/display_manager.h
index bbc228009a7e475cff65f00c995d424ea707764c..25be7c11281b21ef381aa0e4d9f356745626849f 100644
--- a/ash/display/display_manager.h
+++ b/ash/display/display_manager.h
@@ -59,8 +59,6 @@ class ASH_EXPORT DisplayManager : public aura::RootWindowObserver {
 
   bool IsInternalDisplayId(int64 id) const;
 
-  uint64 internal_display_id() const { return internal_display_id_; }
-
   bool UpdateWorkAreaOfDisplayNearestWindow(const aura::Window* window,
                                             const gfx::Insets& insets);
 
@@ -188,8 +186,6 @@ class ASH_EXPORT DisplayManager : public aura::RootWindowObserver {
 
   DisplayList displays_;
 
-  int64 internal_display_id_;
-
   // An internal display cache used when the internal display is disconnectd.
   scoped_ptr<gfx::Display> internal_display_;