Use the icon bounds for all calculations.

- Fixes a drag and drop issue when the dynamic
grid scales icons down, due to the drawable bounds
not being equal to their bitmap sizes.

Change-Id: If7c68b51131de7bac3195a2619e22340f7789432

src/com/android/launcher3/DragSource.java

@@ -30,6 +30,11 @@ public interface DragSource {
      */
     boolean supportsFlingToDelete();
 
+    /*
+     * @return the scale of the icons over the workspace icon size
+     */
+    float getIntrinsicIconScaleFactor();
+
     /**
      * A callback specifically made back to the source after an item from this source has been flung
      * to be deleted on a DropTarget.  In such a situation, this method will be called after