[caching] Allow WebAssembly fetches to use code cache.

Fixes a few problems preventing the WASM cache from working.
- Routes raw resource metadata to the WASM code cache.
- Separates JS and WASM generated code caches. They can't share
  a directory.
- Allow cached metadata to be set on RawResources.

Bug: chromium:719172
Change-Id: I0f3709340948bb25d134504bb03632eb1ce24196
Reviewed-on: https://chromium-review.googlesource.com/c/1255963
Commit-Queue: Bill Budge <bbudge@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Mythri Alle <mythria@chromium.org>
Cr-Commit-Position: refs/heads/master@{#596779}
4 files changed