Video URL:
https://storage.cloud.google.com/chromiumos-test-logs/bugfiles/cr/922253/videoplayback%20(2).mp4?_ga=2.233078422.-967102564.1532641052

This works for me on samus @ 73.0.3681.0 (ToT build).

It seems the file can be selected through long tap, though releasing the finger does not clear the drag-n-drop handle.

After more investigation:

There are some idiosyncrasies with this UI with or without SPM, and some definite problems in SPM:


Non-SPM: 
1. Open Downloads with several files in it
a. Long press a file in Downloads and drag: file can be dragged and copied
b. Long press a file in Downloads and release: file is selected, can not be dragged
c. Long press another file, both files can be dragged and copied; release and both files are selected, can not be dragged.

2: Open 'My Drive'
a. Long tap selects then unselects the file; the file can not be dragged.

3. Switch back to 'Downloads' - behaves as in (1).
The same happens in reverse if the Files app is closed and reopened and 'My Drive' is opened first, then 'Downloads' is opened.


SPM:
1a. Long press selects the file shows a small window for the file. It is not immediately draggable.
1b. Click on the selection window and it can be dragged and copied. Clicking anywhere within the window moves the selection window to that location.
NOTE: No other operation in other windows or the Ash tray can be performed until the item is dragged.
1c. After dragging the selection window and releasing, the selection window disappears. A second item can be long pressed and selected.

2,3. Same as for Non-SPM, long press selects then unselects files, and files can not be dragged in the second top-level folder.

 Issue 922250  has been merged into this issue.

msw, can you take this?

Punting to M-74.

Adding back FileManager, since it seems like files should be draggable even if they are in "My Drive" (2a above). slangley, is that a known issue?