IWYU: missing include for usage of TracingDelegate in ContentBrowserClient

Bug: 41455655
Change-Id: Ia2c948987601f29d5ba15916f1988d86f977f394
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5400904


Reviewed-by: Charlie Reis <creis@chromium.org>
Commit-Queue: José Dapena Paz <jdapena@igalia.com>
Cr-Commit-Position: refs/heads/main@{#1280785}