Service Worker: Layout test for Request HTTP method normalization

TL;DR: Same as XMLHttpRequest

Verify that the Request object from the Fetch API correctly normalizes
method names: DELETE, GET, HEAD, OPTIONS, POST, and PUT are
case-insensitive matched and uppercased, others are left alone.

Spec: http://fetch.spec.whatwg.org/#concept-method-normalize

BUG=401882
R=horo@chromium.org

Review URL: https://codereview.chromium.org/511533002

git-svn-id: svn://svn.chromium.org/blink/trunk@180988 bbb929c8-8fbe-4397-9dbb-9b2b20218538