Support 'URLSearchParams' as the body of a Request

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 577 matching lines @@
             'filename="file.dat"\r\n' +
             'Content-Type: application/octet-stream\r\n' +
             '\r\n' +
             'file content\r\n' +
             '--' + boundary + '--\r\n';
           assert_equals(
             result, expected_body,
             'Creating a Request with FormData body should success.');
         })
       .then(function() {
+          var params = new URLSearchParams();
+          params.append('sample string', '1234567890');
+          request = new Request(URL, {method: 'POST', body: params});
+          return request.text();
+        })
+      .then(function(result) {
+          assert_equals(result, "sample+string=1234567890");
+        })
+      .then(function() {
           t.done();
         })
       .catch(unreached_rejection(t));
     assert_true(request.bodyUsed,
                 'bodyUsed must be true after calling text()');
   }, 'Request body test');
 
 test(function() {
     // https://fetch.spec.whatwg.org/#dom-request
     // Step 20:
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         var req2 = new Request(req);
         assert_true(req.bodyUsed);
         assert_false(req2.bodyUsed);
         return req2.text();
       }).then(function(text) {
         assert_equals(text, '');
       });
   }, 'Consume and pass');
 
 done();