[Reland] WebUI: Turn on ESLint JS presubmit checks for ios/ folder.

Reland notes: Limiting the original change to only apply to JS files
instead of both JS and TS, as there are still TS violations that need to
be fixed. Also confirmed that the following command passes locally
`git cl presubmit --files="ios/*.ts;ios/*.js"`

Also adding CheckChangeOnCommit() which was previously erroneously
missing, causing `git cl presubmit --files=...` to not behave
equivalently to `git cl upload`.

Bug: 40519637
Change-Id: I3be6f2a7bf5d89c32d3ae316e2568baa8b509411
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6287035
Commit-Queue: Demetrios Papadopoulos <dpapad@chromium.org>
Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1423237}