Fix getting an empty thumbnail in reviewing panorama.

The sample size for generating a thumbnail should be calculated in a way
that also considers the case of a portrait image, i.e., height > width.
The SharePopup should also puts the thumbnail of a portrait panorama in
the center of the thumbnail view.

Bug: 5411488

Change-Id: I5e86a91829de77f4694c039bd871e6831f3906cb
2 files changed