Allow addons to inject profiles directly into the profiler via the postMessage API

[gregtatum]

I'm prototyping an addon to visualize Firefox Translations taskcluster runs, but I need a way to inject my profiles directly into the profiler UI.

My code is still a prototype that I got working locally:
https://github.com/gregtatum/taskcluster-webext

Here is an example injection:
https://github.com/gregtatum/taskcluster-tools/blob/main/extension/profiler_content.js

This is an example profile:
https://share.firefox.dev/3GOQafr

[gregtatum]

For fun, here is a 10 hour profile. https://share.firefox.dev/3R1NC1S

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (0ada127) 88.38% compared to head (930d041) 88.39%.

Files	Patch %	Lines
src/actions/receive-profile.js	95.65%	1 Missing ⚠️
src/components/app/ProfileLoader.js	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4835   +/-   ##
=======================================
  Coverage   88.38%   88.39%           
=======================================
  Files         301      301           
  Lines       26876    26910   +34     
  Branches     7268     7286   +18     
=======================================
+ Hits        23754    23786   +32     
- Misses       2906     2908    +2     
  Partials      216      216           

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[mstange]

This is great! I've wanted a way to postMessage profiles into the profiler for a different reason: To make samply work on macOS when Safari is the default browser. Safari doesn't allow network requests from the profiler to localhost (because the profiler is https and localhost is http), so a potential workaround would be to open a localhost page with a button which opens the profiler in a new tab and postMessages the profile into it. The only trouble is the question when to call postMessage - the localhost page can't know when the profiler page is done loading. Oh, and the profiler wouldn't have a way to request symbols. (I suppose the localhost page could send a message channel along with the initial postMessage, as a way to initiate bidirectional communication...)

[gregtatum]

I added a way to poll the page for when it's ready. In an addon it seems like you can just wait a tick and it'll be ready.

[gregtatum]

The codecoverage failure is a false positive as far as I can tell, since most of them are assertions for states that shouldn't happen.

[gregtatum]

I force pushed a new version of the code that removes the mentions of an addon, as this works with a plain webpage (barring any unforeseen CSP issues).

[julienw]

Thanks, this looks interesting!

I left a few comments, tell me what you think!
Especially I don't see if/why the change to the action PROFILE_LOADED adding a dataSource property is needed.

r=me with the comments added and the changes to the PROFILE_LOADED action removed (unless we discussed otherwise).

[julienw]

Mmm, is that one or 2 lines too high? :-)