[Fetch] Body consume function should not set bodyUsed flag.

LayoutTests/http/tests/cachestorage/script-tests/cache-add.js

Index: LayoutTests/http/tests/cachestorage/script-tests/cache-add.js
diff --git a/LayoutTests/http/tests/cachestorage/script-tests/cache-add.js b/LayoutTests/http/tests/cachestorage/script-tests/cache-add.js
index 0f85d120f8f9e280cc50ab5075fe67921aa182c9..27051ee15fcb3f19aa51a4796dd023dbd0948840 100644
--- a/LayoutTests/http/tests/cachestorage/script-tests/cache-add.js
+++ b/LayoutTests/http/tests/cachestorage/script-tests/cache-add.js
@@ -39,14 +39,10 @@ cache_test(function(cache) {
     var request = new Request('../resources/simple.txt', {method: 'POST', body: 'Hello'});
     return request.text()
       .then(function() {
-          assert_true(request.bodyUsed);
+          assert_false(request.bodyUsed);
         })
       .then(function() {
-          return assert_promise_rejects(
-            cache.add(request),
-            new TypeError(),
-            'Cache.add with a Request object with a used body should reject ' +
-            'with a TypeError.');
+          return cache.add(request);
         });
   }, 'Cache.add called with Request object with a used body');