Using color filter when animating the drop target instead to TransitionDrawable

> No more flickering when crossfading between two bitmaps in small duration
> Allows us to control the color directly without depending on the assets

Change-Id: Ie7ed8bb94baf560e9b939cca624ed1bad457732c

src/com/android/launcher3/DeleteDropTarget.java

@@ -43,7 +43,7 @@ public class DeleteDropTarget extends ButtonDropTarget {
         // Get the hover color
         mHoverColor = getResources().getColor(R.color.delete_target_hover_tint);
 
-        setDrawable(R.drawable.remove_target_selector);
+        setDrawable(R.drawable.ic_launcher_remove_normal);
     }
 
     public static boolean supportsDrop(Object info) {