opening local files via DnD creates about:blank tabs rather than opening the file

[kjozwiak]

Test plan

See #15204

Description

Opening files via dragging and dropping in the tab bar opens about:blank tabs rather than opening the files. We've also received similar complaints from the community:

• https://www.reddit.com/r/brave_browser/comments/9bgsot/v023105_for_desktop_has_been_released/e55r5sj

I'm assuming this is another regression from the about:blank security issue that we added into the 0.23.104 release which has caused several about:blank regressions.

Steps to Reproduce

1. ensure that you have a .html or a .txt file saved locally
2. install & launch either 0.23.206 80a5ac1 or 0.23.107 6f2fc65.
3. once brave has launched, load any random website in a tab
4. drop the local file you have saved on top of the above tab and you'll notice that instead of opening the local file, it creates a about:blank tab

Actual result:

macOS Example:

Windows 10 x64 Example:

Expected result:

DnD files into the tab area should be opening the files rather than creating about:blank tabs.

Reproduces how often:

It's 100% reproducible on macOS but not always reproducible on Win.

Brave Version

about:brave info:

Brave: 0.23.206 
V8: 6.9.427.22 
rev: 80a5ac134e251a9cb3565023e2447d6d7b4487a7 
Muon: 8.1.5 
OS Release: 17.7.0 
Update Channel: Release 
OS Architecture: x64 
OS Platform: macOS 
Node.js: 7.9.0 
Brave Sync: v1.4.2 
libchromiumcontent: 69.0.3497.92

Reproducible on current live release:

Yes, currently reproducible on the following build which is the current live version:

Brave: 0.23.107 
V8: 6.8.275.24 
rev: 6f2fc65b3c7db0b260ad154fbef5919902495387 
Muon: 8.0.10 
OS Release: 17.7.0 
Update Channel: Release 
OS Architecture: x64 
OS Platform: macOS 
Node.js: 7.9.0 
Brave Sync: v1.4.2 
libchromiumcontent: 68.0.3440.84

Additional Information

[bsclifton]

cc: @diracdeltas

[bsclifton]

@kjozwiak is this a duplicate of #15134?

[kjozwiak]

@bsclifton they're a bit different but I suspect the fix would probably cover both cases. This particular case also affects .txt, .html and others. #15134 deals with directly clicking on .html files and seeing the about:blank pages. This case deals with opening files by directly dropping them on tabs that have already been created.

Are we going to fix this in this release or should we move it to the 0.23.x Release 7? We're going to need a muon build either way due to #15202. It would be nice to get these fixed. If we're going to fix this in the C69 release, we should probably move #15134 into this milestone as well.

[diracdeltas]

yup, the fix i'm working on for #15134 would also fix this

[kjozwiak]

Thanks @diracdeltas, moved #15134 into this milestone as well 👍

[LaurenWags]

Verified with macOS 10.12.6 using

• 0.23.207 281de88
• Muon 8.1.6
• libchromiumcontent 69.0.3497.100

Verified with macOS 10.13.6 using the following build:

• 0.23.207 281de88
• muon: 8.1.6
• libchromiumcontent: 69.0.3497.100

Verified with Win 10 x64 using the following build:

• 0.23.207 281de88
• muon: 8.1.6
• libchromiumcontent: 69.0.3497.100

However, DnD doesn't seem to be working under Win 10 & Linux. Created #15208.