Fetch: Fix 'body' processing in RequestInit.

third_party/WebKit/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';
 
 test(function() {
     var headers = new Headers;
     headers.set('User-Agent', 'Mozilla/5.0');
     headers.set('Accept', 'text/html');
@@ skipping 730 matching lines @@
                           {method: 'POST',
                            body: new Blob([''], {type: 'Text/Plain'}),
                            headers: [['Content-Type', 'Text/Html']]});
     return req.blob()
       .then(function(blob) {
           assert_equals(blob.type, 'text/html');
           assert_equals(req.headers.get('Content-Type'), 'Text/Html');
         });
   }, 'Extract a MIME type (1)');
 
+promise_test(function(t) {
+    var req = new Request('http://localhost/',
+                          {method: 'POST',
+                           credentials: 'include',
+                           body: 'this is a body'});
+
+    return req.text()
+        .then(t => {
+           assert_equals(t, 'this is a body');
+        });
+  }, 'Credentials and body can both be set.');
+
 done();