Upgrade from Chromium 76.0.3809.87 to Chromium 76.0.3809.100

[bsclifton]

Fixes #5554
Related: brave/brave-core#3099

Submitter Checklist:

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Verified that these changes build without errors on
  • Android
  • iOS
  • Linux
  • macOS
  • Windows
• Verified that these changes pass automated tests (unit, browser, security tests) on
  • iOS
  • Linux
  • macOS
  • Windows
• Ran git rebase master (if needed).
• Ran git rebase -i to squash commits (if needed).
• Tagged reviewers and labelled the pull request as needed.
• Requested a security/privacy review as needed.
• Public documentation has been updated as necessary. For instance:
  • https://github.com/brave/brave-browser/wiki/Deviations-from-Chromium-(features-we-disable-or-remove)
  • https://github.com/brave/brave-browser/wiki/Proxy-redirected-URLs
  • https://github.com/brave/brave-browser/wiki/Fingerprinting-Protection-Mode
  • https://github.com/brave/brave-browser/wiki/Brave%E2%80%99s-Use-of-Referral-Codes
  • https://github.com/brave/brave-browser/wiki/Custom-Headers
  • https://github.com/brave/brave-browser/wiki/Web-compatibility-issues-with-tracking-protection

Test Plan:

Reviewer Checklist:

• New files have MPL-2.0 license header.
• Request a security/privacy review as needed.
• Adequate test coverage exists to prevent regressions.

After-merge Checklist:

• The associated issue milestone is set to the smallest version that the
  changes has landed on.
• All relevant documentation has been updated.

[bsclifton]

macOS failed when fetching from remote (all others passed):
https://staging.ci.brave.com/job/brave-browser-build-pr/job/PR-5556/2/execution/node/199/log/

Restarted job with :
https://staging.ci.brave.com/view/ci/job/brave-core-build-pr/view/change-requests/job/PR-3099/2/console

[bsclifton]

On re-run, Win64 failed:
https://staging.ci.brave.com/job/brave-browser-build-pr/job/PR-5556/4/execution/node/459/log/

But all other platforms passed great. Should be good to go! 😄 👍

[rebron]

Looks good!