#4058: fix race condition on tab load

[twschiller]

What does this PR do?

• Part of No handler registered for RUN_BRICK in contentScript in brick running in target tab #4058
• Moves the onContextInvalidated listener to the contentScriptCore to avoid the messenger registration race condition

Discussion

• @fregante there's still a race in the init() method. If you put a await sleep(1000) as the first line init method, you'll see that you still get the error. That's because the __getTabData method is loading synchronously with the module load, while the registerMessenger is running async.
• I think we need to be able explicitly set the messenger as "ready". Otherwise you'll always run into race conditions with: 1) message registration, 2) brick registration, 3) other content script initialization, etc.

Coordination

• Designate a primary reviewer: @fregante

[codecov-commenter]

Codecov Report

Merging #4061 (5323be2) into main (b6180c8) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##             main    #4061   +/-   ##
=======================================
  Coverage   47.85%   47.85%           
=======================================
  Files         868      868           
  Lines       25872    25872           
  Branches     5361     5361           
=======================================
  Hits        12380    12380           
  Misses      12560    12560           
  Partials      932      932           

Impacted Files	Coverage Δ
src/contentScript/contentScript.ts	0.00% <0.00%> (ø)
src/contentScript/contentScriptCore.ts	0.00% <0.00%> (ø)

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[fregante]

there's still a race in the init() method

Yes that’s why I suggested that this solution was temporary. I'd probably revert this PR in full once the issue is avoided at the root.