Disable cross-app drag/drop

@hides the View constant that designates a drag as cross-app, and also
forcibly ignores that flag on the system_server side even if it's passed
to startDrag() as a literal.

Change-Id: I6f321bdf0389db5bb44131fd0f8d6b92f049be52
diff --git a/core/java/android/view/View.java b/core/java/android/view/View.java
index 378eb21..bbd3e09 100644
--- a/core/java/android/view/View.java
+++ b/core/java/android/view/View.java
@@ -2234,6 +2234,8 @@
      * {@link #startDrag(ClipData, DragShadowBuilder, Object, int)} is called
      * with this flag set, all visible applications will be able to participate
      * in the drag operation and receive the dragged content.
+     *
+     * @hide
      */
     public static final int DRAG_FLAG_GLOBAL = 1;