Revert of Revert "Typecheck JS files for chrome://extensions" (patchset #1 of https://codereview.chromium.org/
508283002/)
Reason for revert:
fixed check_licenses issues
Original issue's description:
> Revert "Typecheck JS files for chrome://extensions"
>
> This reverts commit
405253b7ee22ecb318d3c1ca9187e1e7259e704f.
>
> Caused a liscene failure on android bot:
> http://build.chromium.org/p/chromium.linux/builders/Android%20Builder%20%28dbg%29/builds/64664/steps/check_licenses/logs/stdio
>
> Committed to pending queue: https://chromium.googlesource.com/chromium/src/+/
87b3206
TBR=vitalyp@chromium.org,eroman@chromium.org
NOTREECHECKS=true
NOTRY=true
Review URL: https://codereview.chromium.org/
512003002
Cr-Commit-Position: refs/heads/master@{#292229}