Fixing issue with cancelled drag blocking cell spaces (Issue 5386523)

Change-Id: I9cfc728edeeee2237c21935517107e7a2af49646

src/com/android/launcher2/DragController.java

@@ -361,6 +361,7 @@ public class DragController {
             if (mLastDropTarget != null) {
                 mLastDropTarget.onDragExit(mDragObject);
             }
+            mDragObject.cancelled = true;
             mDragObject.dragComplete = true;
             mDragObject.dragSource.onDropCompleted(null, mDragObject, false);
         }

src/com/android/launcher2/DropTarget.java

@@ -52,6 +52,9 @@ public interface DropTarget {
         /** Post drag animation runnable */
         public Runnable postAnimationRunnable = null;
 
+        /** Indicates that the drag operation was cancelled */
+        public boolean cancelled = false;
+
         public DragObject() {
         }
     }

src/com/android/launcher2/Workspace.java

@@ -3051,6 +3051,9 @@ public class Workspace extends SmoothPagedView
             }
             cellLayout.onDropChild(mDragInfo.cell);
         }
+        if (d.cancelled &&  mDragInfo.cell != null) {
+                mDragInfo.cell.setVisibility(VISIBLE);
+        }
         mDragOutline = null;
         mDragInfo = null;
     }