Fix thumbnails for low framerate Ogg Theora Videos

Instead of a fixed 3 seconds, calculate seek point
based on framerate to fix thumbnails for videos
with lower framerates.

Bug: 47465
Change-Id: I4b2b34408684ac4f8712f39f5b6acd34abcc499e
Merge "Fix thumbnails for low framerate Ogg Theora Videos"