Bug 337304 Prevent context menu and autoscroll indicator popup from being present simultaneously

r=jag sr=neil

suite/common/utilityOverlay.js

@@ -632,6 +632,7 @@ function startScrolling(event)
   addEventListener('mousemove', handleMouseMove, true);
   addEventListener('mouseup', handleMouseUpDown, true);
   addEventListener('mousedown', handleMouseUpDown, true);
+  addEventListener('contextmenu', handleMouseUpDown, true);
   gAutoScrollTimer = setInterval(autoScrollLoop, 10);
   gAccumulatedScrollErrorX = 0;
   gAccumulatedScrollErrorY = 0;
@@ -693,6 +694,7 @@ function stopScrolling()
     removeEventListener('mousemove', handleMouseMove, true);
     removeEventListener('mousedown', handleMouseUpDown, true);
     removeEventListener('mouseup', handleMouseUpDown, true);
+    removeEventListener('contextmenu', handleMouseUpDown, true);
     clearInterval(gAutoScrollTimer);
   }
 }