[Fetch] Request with GET/HEAD method cannot have body

LayoutTests/http/tests/serviceworker/resources/cache-match-worker.js

 importScripts('worker-testharness.js');
 importScripts('/resources/testharness-helpers.js');
 importScripts('override_assert_object_equals.js');
 
 // A set of Request/Response pairs to be used with prepopulated_cache_test().
 var simple_entries = [
   {
     name: 'a',
     request: new Request('http://example.com/a'),
     response: new Response('')
@@ skipping 163 matching lines @@
 prepopulated_cache_test(simple_entries, function(cache, entries) {
     return cache.match(new Request(entries.a.request.url))
       .then(function(result) {
           assert_object_equals(result, entries.a.response,
                                'Cache.match should match by Request.');
         });
   }, 'Cache.match with new Request');
 
 cache_test(function(cache) {
     var request = new Request('https://example.com/foo', {
-        method: 'GET',
+        method: 'POST',
         body: 'Hello world!'
       });
     var response = new Response('Booyah!', {
         status: 200,
         headers: {'Content-Type': 'text/plain'}
       });
 
     return cache.put(request.clone(), response.clone())
       .then(function() {
           assert_false(
@@ skipping 391 matching lines @@
         });
       p = p.then(function() {
           assert_equals(Object.keys(hash).length, entries.length);
         });
 
       return p.then(function() {
           return test_function(cache, hash);
         });
     }, description);
 }