Revive a fetch() test accidentally removed

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

Index: LayoutTests/http/tests/fetch/script-tests/response.js
diff --git a/LayoutTests/http/tests/fetch/script-tests/response.js b/LayoutTests/http/tests/fetch/script-tests/response.js
index e073efa7de9457cdf90f88702b57a1ac35ad9897..3bb470065df4ccc0ea9bffad9e0eace2fb07798d 100644
--- a/LayoutTests/http/tests/fetch/script-tests/response.js
+++ b/LayoutTests/http/tests/fetch/script-tests/response.js
@@ -346,10 +346,18 @@ promise_test(function(t) {
   }, 'MIME type for Blob');
 
 promise_test(function(t) {
-    var res = new Response(new Blob([''], {type: 'Text/Plain'}));
+    var res = new Response(new Blob(['hello'], {type: 'Text/Plain'}));
     return res.blob()
       .then(function(blob) {
           assert_equals(blob.type, 'text/plain');
+          assert_equals(blob.size, 5);
+          assert_equals(res.headers.get('Content-Type'), 'text/plain');
+          return res.blob();
+        }).then(function(blob) {
+          // When we read from a response twice, it returns an empty contents.
+          // But the type should remain.
+          assert_equals(blob.type, 'text/plain');
+          assert_equals(blob.size, 0);
           assert_equals(res.headers.get('Content-Type'), 'text/plain');
         });
   }, 'MIME type for Blob with non-empty type');