Merged 7f4d207c8bd510cd1843ff3e30608f0e5290cb1e
Merged 7819c593e8d7102922d00578ba4b4c8b69a6dce7

Add hash fields to code cache header.

Add payload checksum to code cache data.

BUG=chromium:441896
LOG=N
R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/929283002

Cr-Commit-Position: refs/branch-heads/4.1@{#18}
Cr-Branched-From: 2e08d2a7aa9d65d269d8c57aba82eb38a8cb0a18-refs/heads/candidates@{#25353}