[Performance] Remove redundant map lookups

GetFeatureValueForOrigin is already performant (it's just a ~100 entry
map lookup really) but it's called really frequently and eats up CPU.
Since the default policy is already known by the caller, we can just
pass it into GetFeatureValueForOrigin obviating the need for the map
lookup. This winds up with a significant CPU cost savings (.05% reduced
CPU usage on cnn.com). See bug for more details.

Bug: 448418292
Change-Id: If386dc3c91decc8a4cbc2152363263eda5597930
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7001361
Commit-Queue: Josh Karlin <jkarlin@chromium.org>
Reviewed-by: Ian Clelland <iclelland@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1523513}