Implement up and down UI of slide (UI only. not functional).
Android Studio bug work around.
Implement up, down. Serialize it to JSON.
Implement pop slide. Icon is dummy. Pen hovering icon is not cleared sometime on video.
Check-in for record purpose. Draw hovering icon to viewBmp instead of penCanvas. Not work.
Revert "Check-in for record purpose. Draw hovering icon to viewBmp instead of penCanvas. Not work."

This reverts commit a219eaba0e6ab59edc117f9e3def3a8fd7cb82cb.
Fix scroll and hovering icon. Scrolling is a little strange.
Ignore hovering while animating.
Fix scroll, clear.
Fix undo-redo, do not update viewBmp at onDraw anymore. Sometime broken webm seems produced (from slide insertion? why?).
Fix "move down".
Do not finish CAB after move up or down.

To keep selection, I put id as unique long value that correspond to file as 1 on 1.