[chromecast] Enable chrome://inspect on debug builds in web runtime.

Bug: b/344966095
Test: use chrome://inspect on a Cast device running Disney Plus
Change-Id: I76d02df841c61b4d5bbcaa35732f1fe853b01c00
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5598705


Auto-Submit: Simeon Anfinrud <sanfin@chromium.org>
Commit-Queue: Luke Halliwell <halliwell@chromium.org>
Reviewed-by: Luke Halliwell <halliwell@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1311636}