Clicking through PDF link doesn't open the file

[srirambv]

Test plan

1. Clean install (clear profile, etc)
2. Search for bitcoin pdf
3. Click on the first link; it should load

Description

Clicking through PDF link doesn't open the file

Steps to Reproduce

1. Clean install 0.20.9
2. Search for bitcoin pdf
3. Click on the first link, doesn't open the pdf
4. Ctrl+Click on the link, pdf opens in a new tab

Actual result:
Clicking through PDF link doesn't open the file

Expected result:
Clicking through PDF link should open the file

Reproduces how often:
100%

Brave Version

about:brave info:

Brave	0.20.9
V8	6.3.292.48
rev	b5aec10
Muon	4.5.31
OS Release	4.13.0-21-generic
Update Channel	Beta
OS Architecture	x64
OS Platform	Linux
Node.js	7.9.0
Brave Sync	v1.4.2
libchromiumcontent	63.0.3239.108

Reproducible on current live release:
No

Additional Information

On Linux/Windows it doesn't click through
On macOS, it prompts to download the file when trying to click through the link. Confirmed by @LaurenWags

[petemill]

Looks like the browser-laptop pdfJS.js module correctly identifies that a PDF file should be loaded from the extension, but does not know which tabId to load the pdf file in to, since muon is not providing a tabId via the following in app/filtering.js (line 355)

function registerForHeadersReceived (session, partition) {
  const isPrivate = module.exports.isPrivate(partition)
  session.webRequest.onHeadersReceived(function (details, muonCb) {
...

details.tabId, which is passed to pdfJS, which then calls appActions.loadURL with the pdf viewer location, is -1

[bsclifton]

@kjozwiak @LaurenWags this is a weird one.

Please do feel free to try the steps above and make sure it works... but if the issue isn't present in existing 0.19.x release, perhaps we should move this back to 0.20.x

[kjozwiak]

@bsclifton I couldn't reproduce this with the the current 0.19.123 release so it seems like this was a regression within the 0.20.x milestone. We ran through the three different platforms and it looks like it's working fine so I'm okay with adding this into this milestone. I'm assuming we got this fix for free when we bumped muon?

Thoughts?

[bsclifton]

Moving back to 0.20.x - this may have never been a problem in 0.19.x... but there was a related Muon change (which is why I pulled to 0.19.x)

[kjozwiak]

Clearing the flags as these were tested against 0.19.124. As mentioned above, this wasn't a regression within 0.19.x so this issue was moved back into the 0.20.x milestone.