Process FOLLOWS_FROM spans in TraceView

[rubenvp8510]

Which problem is this PR solving?

• This fixes Timeline visualization regression #333

Short description of the changes

• I noticed that there is FOLLOWS_FROM attributes on some spans that wasn't take into account when the indentation of the spans is computes on the TreeView.

Not sure if this is the proper way of handling this, I left two comments for two assumptions that I did. if some of the maintainers can review please. @tiffon @everett980

Thanks!

[codecov]

Codecov Report

Merging #335 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #335      +/-   ##
==========================================
+ Coverage   83.17%   83.18%   +0.01%     
==========================================
  Files         145      145              
  Lines        3221     3224       +3     
  Branches      656      658       +2     
==========================================
+ Hits         2679     2682       +3     
  Misses        434      434              
  Partials      108      108

Impacted Files	Coverage Δ
...ts/TracePage/TraceTimelineViewer/SpanTreeOffset.js	100% <100%> (ø)	⬆️

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[tiffon]

I left a comment with a suggestion. What do you think?

[rubenvp8510]

I like the algorithm you put in the comments, simpler that mine, at the beginning I thought we will give an special treatment to the FOLLOWS_FROM, that is why I split it in two different things, but after an analysis of my implementation and your code it seems like from the UI perspective (or at least for this view) we won't do a distinction. Correct me if this is wrong.

I'll simplify my code.

[rubenvp8510]

I also think that we need to put some tests for this, to avoid regressions.

[rubenvp8510]

@tiffon @everett980 I added one test to take FOLLOWS_FROM into account. I think this is ready for another review, if there is no more comments and you decide it's ok, then it is ready for merge.

[tiffon]

Looks great, thanks! 👍