[gin] Removing file validation.

Removes extra v8 snapshot and natives validation on Windows. This was
added a while ago to track down a bug with corrupted v8 files.
This is a relanding of:
https://codereview.chromium.org/2103903002/

BUG=501799

Review-Url: https://codereview.chromium.org/2680653002
Cr-Commit-Position: refs/heads/master@{#448646}
4 files changed