Unable to open some PDFs

[LaurenWags]

Test plan

1. Go to about:preferences#extensions and verify you are on PDF.js version 1.9.457
2. Navigate to http://www.mckinsey.com/business-functions/mckinsey-analytics/our-insights/how-artificial-intelligence-can-deliver-real-value-to-companies?utm_content=buffer64f12&utm_medium=social&utm_source=linkedin.com&utm_campaign=buffer
3. Locate the 'Full Report (PDF ~3MB)' button (near the top)
4. Click on the button.

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• Did you search for similar issues before submitting this one?
  Yes

• Describe the issue you encountered:
  When navigated to http://www.mckinsey.com/business-functions/mckinsey-analytics/our-insights/how-artificial-intelligence-can-deliver-real-value-to-companies?utm_content=buffer64f12&utm_medium=social&utm_source=linkedin.com&utm_campaign=buffer if you click on the 'Full Report (PDF ~3MB)' button, page opens up as a PDF but no PDF is displayed.

• Platform (Win7, 8, 10? macOS? Linux distro?):
  MacOS

• Brave Version (revision SHA):
  Brave | 0.18.29
  rev | 85f059d
  Muon | 4.3.16

• Steps to reproduce:

  1. Navigate to http://www.mckinsey.com/business-functions/mckinsey-analytics/our-insights/how-artificial-intelligence-can-deliver-real-value-to-companies?utm_content=buffer64f12&utm_medium=social&utm_source=linkedin.com&utm_campaign=buffer
  2. Locate the 'Full Report (PDF ~3MB)' button (near the top)
  3. Click on the button.

• Actual result:
  Page displays PDF viewer but no PDF is displayed.

• Expected result:
  PDF should be displayed.

• Will the steps above reproduce in a fresh profile? If not what other info can be added?
  Yes

• Is this an issue in the currently released version?
  Yes

• Can this issue be consistently reproduced?
  Yes

• Extra QA steps:

  1. When you do this on Chrome, the PDF is downloaded and then you can open in Chrome or other source.

• Screenshot if needed:
  

• Any related issues:

[LaurenWags]

Other PDFs (http://www.orimi.com/pdf-test.pdf or navigate to https://basicattentiontoken.org/faq/#meaning and click Download the Whitepaper) display without issue.

[luixxiul]

Reproduced:

pdf.worker.js:342 Uncaught (in promise) Error: Bad end offset: 5510192
    at error (pdf.worker.js:342)
    at assert (pdf.worker.js:353)
    at ChunkedStream_onReceiveData [as onReceiveData] (pdf.worker.js:15019)
    at ChunkedStreamManager_onReceiveData [as onReceiveData] (pdf.worker.js:15361)
    at ChunkedStreamManager.<anonymous> (pdf.worker.js:15240)
    at <anonymous>

[diracdeltas]

I believe this is an issue in https://github.com/mozilla/pdf.js because the problem also occurs in Chrome with the pdf.js extension (version 1.8.557)

firefox offers to download the file instead of opening it

[diracdeltas]

found a way to fix it in brave/pdf.js#3