Adding support for keyboard based drag and drop

For keyboard DnD, we use Accessible DnD implementation.
A placeholder FloatingView draws the focus indicator
for the virtual views

Test: Visible
Bug: 178781566
Change-Id: I632fc7377dffa1e05e3f0a9c3ad18641deb5a1a4
diff --git a/src/com/android/launcher3/CellLayout.java b/src/com/android/launcher3/CellLayout.java
index 2809bd5..452207d 100644
--- a/src/com/android/launcher3/CellLayout.java
+++ b/src/com/android/launcher3/CellLayout.java
@@ -312,6 +312,13 @@
         }
     }
 
+    /**
+     * Returns the currently set accessibility delegate
+     */
+    public DragAndDropAccessibilityDelegate getDragAndDropAccessibilityDelegate() {
+        return mTouchHelper;
+    }
+
     @Override
     public boolean dispatchHoverEvent(MotionEvent event) {
         // Always attempt to dispatch hover events to accessibility first.