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

LayoutTests/http/tests/fetch/script-tests/request.js

 if (self.importScripts) {
   importScripts('../resources/fetch-test-helpers.js');
 }
 
 var URL = 'https://www.example.com/test.html';
 
 function size(headers) {
   var count = 0;
   for (var header of headers) {
     ++count;
@@ skipping 366 matching lines @@
                  'Request should not be flagged as used if it has not been ' +
                  'consumed.');
     assert_throws(new TypeError(), function() { new Request(req); },
                   'Request cannot be constructed with a request that has ' +
                   'been flagged as used.');
     assert_throws(new TypeError(), function() { req.clone(); },
                   'Request.clone: If used flag is set, throw a TypeError.');
   },
   'Request construction behavior regarding "used" body flag and exceptions.');
 
+
+// Spec: https://fetch.spec.whatwg.org/#dom-request
+// Step 21:
+// If request's method is `GET` or `HEAD`, throw a TypeError.
+promise_test(function() {
+    var headers = new Headers;
+    headers.set('Content-Language', 'ja');
+    ['GET', 'HEAD'].forEach(function(method) {
+        assert_throws(
+          {name: 'TypeError'},
+          function() {
+            new Request(URL,
+                        {method: method,
+                         body: new Blob(['Test Blob'], {type: 'test/type'})
+                        });
+          },
+          'Request of GET/HEAD method cannot have RequestInit body.');
+      });
+  }, 'Request of GET/HEAD method cannot have RequestInit body.');
+
 promise_test(function() {
     var headers = new Headers;
     headers.set('Content-Language', 'ja');
     var req = new Request(URL, {
-        method: 'GET',
+        method: 'POST',
         headers: headers,
         body: new Blob(['Test Blob'], {type: 'test/type'})
       });
     var req2 = req.clone();
     // Change headers and of original request.
     req.headers.set('Content-Language', 'en');
     assert_equals(req2.headers.get('Content-Language'), 'ja',
                   'Headers of cloned request should not change when ' +
                   'original request headers are changed.');
 
@@ skipping 146 matching lines @@
           {name: 'TypeError'},
           function() {
             new Request('http://localhost/',
                          {headers: [['X-Fetch-Test', value]]});
           },
           'new Request with headers with an invalid value should throw');
       });
   }, 'Request throw error test');
 
 done();