Tracker: Reimplement BSlowContextPopup as BPopUpNavMenu.

BSlowContextPopup was mostly a duplicate class of BNavMenu
only on top of BPopUpMenu instead of BMenu. Now, BPopUpNavMenu
just subclasses BNavMenu and adds the few features of BPopUpMenu
neccessary.

Drag-and-drop of files using the pop-up nav menu seems to still work fine.

Change-Id: Ic1f49c5bed60fff7a3076a22f74aebc6eba51d57

headers/private/tracker/NavMenu.h

@@ -148,6 +148,30 @@ protected:
 	TrackingHookData fTrackingHook;
 };
 
+
+class BPopUpNavMenu : public BNavMenu {
+public:
+	BPopUpNavMenu(const char* title);
+	~BPopUpNavMenu();
+
+	void ClearMenu();
+
+	void Go(BPoint where);
+	bool IsShowing() const;
+
+protected:
+	BPoint ScreenLocation();
+
+private:
+	void _WaitForTrackThread();
+	static int32 _TrackThread(void* menu);
+
+private:
+	BPoint fWhere;
+	thread_id fTrackThread;
+};
+
+
 //	Spring Loaded Folder convenience routines
 //		used in both Tracker and Deskbar
 #ifndef _IMPEXP_TRACKER