blink/bindings: Make foreground and background compression mutually exclusive.

Cleans up feature flags for string parking, making foreground and background
compression mutually exclusive. Compression on memory pressure is kept in both
cases.

This does not remove background compression, as the foreground one is still
experimental, whereas the background one has been validated by deb/beta/stable
experiments.

Bug: 877044, 924164
Change-Id: I79b65e6d0073b18a704055e0cfeb54ba451e20c2
Reviewed-on: https://chromium-review.googlesource.com/c/1458200
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Benoit L <lizeb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#629965}
2 files changed