Upstream service worker `fetch` test to WPT

**fetch-request-css-cross-origin-mime-check**

Update resource file paths as appropriate and use HTTPS version of
absolute URLs.

**fetch-request-fallback**

Both the Chromium version and upstream version of this test cover the
following conditions:

- same origin XHR should succeed
- CORS-unsupported other origin XHR should fail
- CORS-supported other origin XHR should succeed
- redirected XHR should succeed
- XHR which is redirected to CORS-unsupported other origin should fail
- XHR which is redirected to CORS-supported other origin should succeed

However, the Chromium version includes additional tests for image
requests:

- image request should succeed
- other origin image request should succeed
- CORS-unsupported other origin image request should fail
- CORS-supported other origin image request should succeed
- redirected image request should succeed
- image request which is redirected to other origin should succeed
- image request which is redirected to CORS-unsupported other origin should fail
- image request which is redirected to CORS-supported other origin should succeed

The two versions differ significantly in test structure, as well. Adopt
the Chromium version's structure because that implements more granular
assertion messages.

BUG=688116
R=mek@chromium.org

Review-Url: https://codereview.chromium.org/2858933003
Cr-Commit-Position: refs/heads/master@{#470248}
13 files changed