Line break not recognized in alert window

[srirambv]

Test plan

#10835 (comment)

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• Did you search for similar issues before submitting this one?
  Yes, mostly a dupe issue

• Describe the issue you encountered:
  Line break not recognized in alerts

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

• Brave Version (revision SHA):

Brave	0.17.19
rev	4e46480
Muon	4.1.9

• Steps to reproduce:

  1. Visit https://jsfiddle.net/9o5tmgst/1/
  2. See horribly formatted text on the alert window

• Actual result:
  Line break not recognized in alert window

• Expected result:
  Should respect line breaks and show content properly

• 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, could be a regression so needs triage

• Can this issue be consistently reproduced?
  Yes

• Extra QA steps:
  1.
  2.
  3.

• Screenshot if needed:
  
  

• Any related issues:
  cc: @luixxiul @bsclifton