[Cache API] Add Cache and CacheStorage IDL definitions

[Cache API] Add Cache and CacheStorage IDL definitions
https://bugs.webkit.org/show_bug.cgi?id=175201
<rdar://problem/33738001>

Unreviewed.
Rebasing test expectations after http://trac.webkit.org/changeset/220310.

Patch by Youenn Fablet <youenn@apple.com> on 2017-08-05

* web-platform-tests/service-workers/cache-storage/serviceworker/cache-add.https-expected.txt:
* web-platform-tests/service-workers/cache-storage/serviceworker/cache-delete.https-expected.txt:
* web-platform-tests/service-workers/cache-storage/serviceworker/cache-keys.https-expected.txt:
* web-platform-tests/service-workers/cache-storage/serviceworker/cache-match.https-expected.txt:
* web-platform-tests/service-workers/cache-storage/serviceworker/cache-matchAll.https-expected.txt:
* web-platform-tests/service-workers/cache-storage/serviceworker/cache-put.https-expected.txt:
* web-platform-tests/service-workers/cache-storage/serviceworker/cache-storage-keys.https-expected.txt:
* web-platform-tests/service-workers/cache-storage/serviceworker/cache-storage-match.https-expected.txt:
* web-platform-tests/service-workers/cache-storage/serviceworker/cache-storage.https-expected.txt:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@220319 268f45cc-cd09-0410-ab3c-d52691b4dbfc