Switch to standard integer types in url/.

BUG=138542
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Review URL: https://codereview.chromium.org/1542703002

Cr-Commit-Position: refs/heads/master@{#366454}
diff --git a/url/gurl_unittest.cc b/url/gurl_unittest.cc
index 18aa2ae..1320609 100644
--- a/url/gurl_unittest.cc
+++ b/url/gurl_unittest.cc
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include <stddef.h>
+
 #include "base/macros.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "url/gurl.h"