[api-minor] Validate the workerPort/workerSrc options

[Snuffleupagus]

Ensure that users cannot provide incorrect values when trying to set the global worker-options.
This patch was prompted by occasionally seeing users manually loading the pdf.worker.mjs-file and then assigning it to the workerSrc-option, something that obviously doesn't make sense and will cause fake-workers to be used (with poor performance as a result).

[Snuffleupagus]

/botio test

[moz-tools-bot]

From: Bot.io (Linux m4)

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Received

Command cmd_test from @Snuffleupagus received. Current queue size: 0

Live output at: http://54.241.84.105:8877/8b3d79942554442/output.txt

[moz-tools-bot]

From: Bot.io (Windows)

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Received

Command cmd_test from @Snuffleupagus received. Current queue size: 0

Live output at: http://54.193.163.58:8877/9a90b119a0ead17/output.txt

[moz-tools-bot]

From: Bot.io (Linux m4)

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Failed

Full output at http://54.241.84.105:8877/8b3d79942554442/output.txt

Total script time: 24.31 mins

• Unit tests: Passed
• Integration Tests: Passed
• Regression tests: FAILED

  different ref/snapshot: 17
  different first/second rendering: 1

Image differences available at: http://54.241.84.105:8877/8b3d79942554442/reftest-analyzer.html#web=eq.log

[moz-tools-bot]

From: Bot.io (Windows)

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Failed

Full output at http://54.193.163.58:8877/9a90b119a0ead17/output.txt

Total script time: 37.95 mins

• Unit tests: Passed
• Integration Tests: Passed
• Regression tests: FAILED

  different ref/snapshot: 26

Image differences available at: http://54.193.163.58:8877/9a90b119a0ead17/reftest-analyzer.html#web=eq.log

[calixteman]

LGTM. Thank you.

[mbrevda]

It might have been worth waiting for a major revision for this change as it is likely to break lots of deploys. "make sense" or not, many include/require the worker and pass that as the value, possibly due to this being one of the top hits on Google. Additionally, due to the way bundlers are used these days, it's quite unergonomic and unnatural to include part of a library by "building" (i.e. copying) it separately.

For anyone dealing with this issue:

• the value of pdfjsLib.GlobalWorkerOptions.workerSrc should to be a string.
• If node_modules aren't available at run time (e.g. only built files are deployed), the worker at node_modules/pdfjs-dist/build/pdf.worker.js must be included by copying it manually or via a bundler.
• Set pdfjsLib.GlobalWorkerOptions.workerSrc to the path where the worker can be found.