Accessibility: Folder drag and drop fixes

> Do not allow empty cells on the last page to be click targets
> Make drop targets accessible
> Do not close folder on tap outside

Change-Id: I7cae20e45097092f41408b888e20b6c40c17d981
diff --git a/src/com/android/launcher3/Folder.java b/src/com/android/launcher3/Folder.java
index a282805..b1aba63 100644
--- a/src/com/android/launcher3/Folder.java
+++ b/src/com/android/launcher3/Folder.java
@@ -275,6 +275,9 @@
         for (int i = 0; i < mContent.getChildCount(); i++) {
             mContent.getPageAt(i).enableAccessibleDrag(enable, CellLayout.FOLDER_ACCESSIBILITY_DRAG);
         }
+
+        mFooter.setImportantForAccessibility(enable ? IMPORTANT_FOR_ACCESSIBILITY_NO_HIDE_DESCENDANTS :
+            IMPORTANT_FOR_ACCESSIBILITY_AUTO);
         mLauncher.getWorkspace().setAddNewPageOnDrag(!enable);
     }