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

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

 if (self.importScripts) {
   importScripts('../resources/fetch-test-helpers.js');
 }
 
 function size(headers) {
   var count = 0;
   for (var header of headers) {
     ++count;
   }
   return count;
@@ skipping 337 matching lines @@
     var res = new Response('hello');
     var body = res.body;
     var clone = res.clone();
     assert_not_equals(res.body, body);
     assert_not_equals(res.body, clone.body);
     assert_not_equals(body, clone.body);
     assert_throws({name: 'TypeError'}, function() { body.getReader(); });
     return Promise.all([res.text(), clone.text()]).then(function(r) {
         assert_equals(r[0], 'hello');
         assert_equals(r[1], 'hello');
+        return Promise.all([res.text(), clone.text(), res.clone().text()]);
+      }).then(function(r) {
+        assert_equals(r[0], '');
+        assert_equals(r[1], '');
+        assert_equals(r[2], '');
       });
   }, 'Clone on Response (text)');
 
 promise_test(function(t) {
     var res = new Response('hello');
     var body = res.body;
     var clone = res.clone();
     assert_not_equals(res.body, body);
     assert_not_equals(res.body, clone.body);
     assert_not_equals(body, clone.body);
     assert_throws({name: 'TypeError'}, function() { body.getReader(); });
     var reader1 = res.body.getReader();
     var reader2 = clone.body.getReader();
     return Promise.all([consume(reader1), consume(reader2)]).then(function(r) {
         assert_equals(decode(r[0]), 'hello');
         assert_equals(decode(r[1]), 'hello');
+        return Promise.all([res.text(), clone.text(), res.clone().text()]);
+      }).then(function(r) {
+        assert_equals(r[0], '');
+        assert_equals(r[1], '');
+        assert_equals(r[2], '');
       });
   }, 'Clone on Response (manual read)');
 
 promise_test(function(t) {
     var res = new Response('hello');
     var clone = res.clone();
     res.body.cancel();
     return Promise.all([res.text(), clone.text()]).then(function(r) {
         assert_equals(r[0], '');
         assert_equals(r[1], 'hello');
@@ skipping 118 matching lines @@
         assert_equals(texts[0], '');
         assert_equals(texts[1], '');
         return res.body.getReader().read();
       }).then(function(r) {
         assert_true(r.done);
         assert_equals(r.value, undefined);
       });
   }, 'Read after text()');
 
 done();