JS iloop policing needs to be enhanced

[alexwykoff]

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

• Describe the issue you encountered:
  When visiting https://www.extremetech.com/internet/220696-forbes-forces-readers-to-turn-off-ad-blockers-promptly-serves-malware the CPU spikes and holds for a considerably long period of time.

• Platform (Win7, 8, 10? macOS? Linux distro?):
  Tested on OS X

• Brave Version (revision SHA):
  0.14.0 RC2 (b00c5d9)

• Steps to reproduce:

  1. Visit b00c5d9
  2. Check CPU usage

• Actual result:
  The page should load quickly and CPU usage should be nominal (certainly not 100% for more than a couple seconds)

• Expected result:
  The CPU usage stays above 100% (for multicore systems) for a considerably long time

• 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?
  0.13.5 appears to behave better

• Can this issue be consistently reproduced?
  Yes

• Extra QA steps:
  1.
  2.
  3.

• Screenshot if needed:

• Any related issues:

[bsclifton]

Moving to 0.14.3

[alexwykoff]

Can't reproduce on latest, but if we see it again, we can pull it into a near milestone