Merge "Revised the OnDragListener and onDragEvent API documentation." am: 629810015f am: b38f3d7744 am: 8ad9969307

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1907031

Change-Id: I10d1576b26e8c4eebfc78eb292e07ab2ccf5d813