(Native American English speaker here.)
As J.R.'s answer says, "track" in "the C++ track" at a conference means a sequence of talks with a common, broadly defined topic. Here's some explanation of how that relates to the other senses of the word "track".
The primary meaning of "track" is the mark left in the ground by someone or something as it moved along, implying that you can follow the same path by following the tracks. There is a strong implication that the tracks go in some sort of a line. For example, here are some "tire tracks":
A secondary, extended meaning, which is more common than the primary meaning, is a path that has been consciously designed to be followed. For example, "train tracks" physically guide trains to move along a certain path. When people or horses run races, they usually do so on a "race track".
When I go to a conference and see the "tracks" listed on the schedule, I can't help but imagine that each track is a straight path through the conference, parallel to the other tracks, and that the people attending the talks of one track are something like a herd of cattle, but moving along somewhat more deliberately and having the ability to choose to jump to another track at any time.