Show React version

[taneliang]

From Brian's 17 July email and doc:

Show lane labels and React version in the UI somewhere

• Lane labels: we may want to wait until Fix performance issues likely caused by unnecessary renders #50 is done in case we want to use WebGL. (Update: Reimplement canvas using view classes #80 implemented a view system and is merged; no longer blocking)
• React version: blocked by Add React version number to profiling marks react#35 (Update: no longer blocking; this was implemented in Add ReactVersion to SchedulingProfiler render scheduled marks facebook/react#19553)

[kartikcho]

Hey @bvaughn, what do you think about keeping lane labels in the tooltip (as it is right now) instead of drawing labels at the start of a lane?

It will take up some valuable space on the left when we port it to Devtools. Adding labels might also make the Devtools UI look too 'packed' in my opinion.

I think the current tooltip does a good job of showing lane information. If we still want to put emphasis on the lane info, we can try moving it to the top of the tooltip or make the font bold.

Screenshot of the current tooltip:

[bvaughn]

Good call. It's probably fine to keep the labels in the tooltip for now– particularly since we don't have anything meaningful to show for them (other than the number). 😄