Refactor scales in TimelineTicks (#3278)
Refactor scales in TimelineTicks (#3278)

* Refactor scales in TimelineTicks

After a discussion with Carsten, I'm simplifying scales' logic to be
easy to understand.

Also I'm erasing "15s" and "15min", because they break a desired property.

* Fixup: Comment
google/orbit,google/orbit,google/orbit,google/orbit