Using GCM v4.3 on Samsung S5 running Android 6.0.1, I added two portrait orientation photos taken with the phone camera. They appear fine on GCM on the phone.
Also, when I selected the photos in GCM before adding them they were displayed rotated 90 degrees anti-clockwise.
When I look in GC on MacBook Pro they are both rotated 90 degrees anti-clockwise.