Blink already has code for handling invalid cached data. The attached test
ensures that cached data is gracefully rejected if it cannot be used.

This also unifies parser cache and code cache handling.

R=yangguo@chromium.org
BUG=439889
LOG=N

Review URL: https://codereview.chromium.org/781203003

Cr-Commit-Position: refs/heads/master@{#25708}