[Fetch] Request.clone() should reflect body consumption.

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

Index: LayoutTests/http/tests/fetch/script-tests/request.js
diff --git a/LayoutTests/http/tests/fetch/script-tests/request.js b/LayoutTests/http/tests/fetch/script-tests/request.js
index 7e16329c30e3999b4f9d8d6f590641ff4e42c23e..ed52f68729d03e4fef976fd0353b8694f3f9a80d 100644
--- a/LayoutTests/http/tests/fetch/script-tests/request.js
+++ b/LayoutTests/http/tests/fetch/script-tests/request.js
@@ -482,6 +482,9 @@ promise_test(function() {
       }).then(function(texts) {
         assert_equals(texts[0], '', 'The body is consumed.');
         assert_equals(texts[1], '', 'The body is consumed.');
+        return req.clone().text();
+      }).then(function(text) {
+        assert_equals(text, '', 'The body was consumed before cloned.');
       });
   }, 'Test clone behavior with loading content from Request.');