Auto open/close drawer as drag shadow enters/exits the drawer.

Also changed the spring load timeout to 1.5 seconds instead.

Bug: 31116400
Change-Id: Id4c82f48724ec480159c512d4149f38f9374b278
diff --git a/src/com/android/documentsui/ItemDragListener.java b/src/com/android/documentsui/ItemDragListener.java
index 2d67ff9..bb20909 100644
--- a/src/com/android/documentsui/ItemDragListener.java
+++ b/src/com/android/documentsui/ItemDragListener.java
@@ -40,7 +40,7 @@
     private static final String TAG = "ItemDragListener";
 
     @VisibleForTesting
-    static final int SPRING_TIMEOUT = 1000;
+    static final int SPRING_TIMEOUT = 1500;
 
     protected final H mDragHost;
     private final Timer mHoverTimer;
@@ -78,6 +78,7 @@
     }
 
     private void handleEnteredEvent(View v, DragEvent event) {
+        mDragHost.onDragEntered(v);
         @Nullable TimerTask task = createOpenTask(v, event);
         if (task == null) {
             return;
@@ -162,5 +163,11 @@
          * @param v the view being hovered
          */
         void onViewHovered(View v);
+
+        /**
+         * Notifies right away when drag shadow enters the view
+         * @param v the view which drop shadow just entered
+         */
+        void onDragEntered(View v);
     }
 }