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`Sec-Fetch-Dest` header for both manifests and resources should be `empty` for
the requests called from application cache according to step 4 and 18.3 of
https://html.spec.whatwg.org/#application-cache-download-process:
```
4. Let request be a new request whose url is manifest URL, client is null,
destination is the empty string, referrer is "no-referrer", synchronous flag is
set, credentials mode is "include", and whose use-URL-credentials flag is set.

18.3. Let request be a new request whose url is URL, client is null,
destination is the empty string, origin is manifest URL's origin, referrer is
"no-referrer", synchronous flag is set, credentials mode is "include",
use-URL-credentials flag is set, and redirect mode is "manual".
```

Bug: 1024198
Change-Id: I6566cead95f995089685fc8eed9635d82e3d4d81
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1926478
Commit-Queue: Yifan Luo <lyf@google.com>
Reviewed-by: Chase Phillips <cmp@chromium.org>
Reviewed-by: Mike West <mkwst@chromium.org>
Reviewed-by: Marijn Kruisselbrink <mek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#719137}