Update FetchLater implementation to match latest proposal
This CL updates the trivial parts of the implementation to match the
the "Deferred fetching" algorithm, i.e. not including any changes
to calculate "available deferred fetching quota", which will be done in
the next CL.
Bug: 40276121
Change-Id: Iea58520faf0cfc26db0318b5d08016f6efa9be75
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6012267
Reviewed-by: Adam Rice ricea@chromium.org
Commit-Queue: Ming-Ying Chung mych@chromium.org
Cr-Commit-Position: refs/heads/main@{#1385544}