Disable text autosizing in extension popups

Blink's text autosizing is enabled on all Android platforms. It turned
out that it is fundamentally incompatible with frame autoresizing that
we use for extension popups, causing DCHECK crashes
(https://crbug.com/422896512#comment9).

This patch ensures to disable text autosizing in extension popups. It
takes effect only on Android because it is the only platform where text
autosizing is used.

An alternative approach would be to disable text autosizing entirely on
Desktop Android, not limited to extension popups. This seems reasonable
as there is no reason to differentiate browsing experience between
Desktop Android and other desktop platforms, but the attempt
(crrev.com/c/6656621) is becoming yak shaving as reviewers tend to ask
to expand the scope (e.g. conditioning with the desktop user-agent,
which would affect phones when Desktop Site is requested). To prevent
the controversial change from being a blocker of the extension UI, this
patch targets the extension popup window only.

Bug: 422896512
Change-Id: I1088de4399bc54c7a346cf2590ecee7165542861
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6666904
Reviewed-by: James Cook <jamescook@chromium.org>
Commit-Queue: Shuhei Takahashi <nya@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1478876}