[Fetch API] Reflect spec changes of bodyUsed property

third_party/WebKit/LayoutTests/http/tests/fetch/script-tests/fetch.js

 if (self.importScripts) {
   importScripts('../resources/fetch-test-helpers.js');
 }
 
 promise_test(function(t) {
     return fetch('http://')
       .then(
         t.unreached_func('fetch of invalid URL must fail'),
         function() {});
   }, 'Fetch invalid URL');
@@ skipping 338 matching lines @@
 test(function(t) {
     function runInfiniteFetchLoop() {
       fetch('dummy.html')
         .then(function() { runInfiniteFetchLoop(); });
     }
     runInfiniteFetchLoop();
   },
   'Destroying the execution context while fetch is happening should not ' +
   'cause a crash.');
 
+test(t => {
+    var req = new Request('/', {method: 'POST', body: ''});
+    fetch(req);
+    assert_true(req.bodyUsed);
+}, 'Calling fetch() disturbs body if not null');
+
+test(t => {
+    var req = new Request('/', {method: 'POST'});
+    fetch(req);
+    assert_false(req.bodyUsed);
+}, 'Calling fetch() doesn\'t disturb body if null');
+
 done();