GitLab

Adds a function to CastMetricsServiceDelegate that Cast embedders can
override to set platform-specific limits for local metrics storage.

Also cleans up changes from https://crrev.com/c/2505741 to use
`constexpr` and multiples of 1024 for default values for consistency.

Bug: b/172356230
Test: metrics_unittests
Test: cast_metrics_unittest
Change-Id: Ib920e4438baf56dff64bcca3f9bcabca77fd354e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2518833Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Reviewed-by: Michael Spang <spang@chromium.org>
Commit-Queue: Akira Baruah <akirabaruah@google.com>
Cr-Commit-Position: refs/heads/master@{#824678}