Background: avoid 100% CPU usage

* There was an infinite exchange of messages between
  the main window and the BackgroundView.
* Fixes #11996.

src/preferences/backgrounds/Backgrounds.cpp

@@ -30,7 +30,6 @@ public:
 							BackgroundsWindow();
 
 			void			RefsReceived(BMessage* message);
-			void			MessageReceived(BMessage* message);
 
 protected:
 	virtual	bool			QuitRequested();
@@ -70,6 +69,7 @@ BackgroundsApplication::MessageReceived(BMessage* message)
 {
 	const void *data;
 	ssize_t size;
+
 	if (message->WasDropped() && message->FindData("RGBColor", B_RGB_COLOR_TYPE,
 			&data, &size) == B_OK) {
 		// This is the desktop telling us that it was changed by a color drop
@@ -125,13 +125,6 @@ BackgroundsWindow::RefsReceived(BMessage* message)
 }
 
 
-void
-BackgroundsWindow::MessageReceived(BMessage* message)
-{
-	BMessenger(fBackgroundsView).SendMessage(message);
-}
-
-
 bool
 BackgroundsWindow::QuitRequested()
 {