Temporarily revert runtime decoder registration.

Some builds in Google3 can't find SkSharedMutex at link time.

This reverts commit ff7006ff8082a6f4298cc9f32acc726535d93711.
This reverts commit 05f45b21b72fdf738986ea428346f2fbec8444d8.

Change-Id: I889e9a3169cf017b8d5daacf75099663fc996d73
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/210785
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
3 files changed