Bug 1527283 [wpt PR 15340] - XMLSerializer: Fix prefixed attribute serialization, a=testonly

Automatic update from web-platform-tests
XMLSerializer: Fix prefixed attribute serialization

... in a case where its owner element has xmlns:prefix of which prefix
is same as the attribute and namespace is not same as the attribute.

e.g.
  el.setAttributeNS("uri1", "p:n", "v");
  el.setAttributeNS(XMLNS_URI, "xmlns:p", "uri2");

ShouldAddNamespaceAttribute() checked only existence of xmlns:prefix in
the element, but we should check existence of (prefix, namespace URI)
pair in the scope according to the specification.

So, this CL adds 'recording the namespace information' step [1] defined
by the specification, and ShouldAddNamespaceAttribute() checks all
available prefixes in the scope.

[1] https://w3c.github.io/DOM-Parsing/#recording-the-namespace

Bug: 929035
Change-Id: I575e8f652ae45f7583202443cc72d5afe5faf59d
Reviewed-on: https://chromium-review.googlesource.com/c/1460643
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Commit-Queue: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#631058}

--

wpt-commits: 265330b7d26194cb60157a18ac399127d21f6b99
wpt-pr: 15340

testing/web-platform/tests/domparsing/XMLSerializer-serializeToString.html

@@ -55,6 +55,22 @@ test(function() {
     '<root attr="&#xD;"/>', '<root attr="&#13;"/>']);
 }, 'check XMLSerializer.serializeToString escapes attribute values for roundtripping');
 
+test(function() {
+  const root = (new Document()).createElement('root');
+  root.setAttributeNS('uri1', 'p:foobar', 'value1');
+  root.setAttributeNS('http://www.w3.org/2000/xmlns/', 'xmlns:p', 'uri2');
+  const xmlString = (new XMLSerializer()).serializeToString(root);
+  assert_equals(xmlString, '<root xmlns:ns1="uri1" ns1:foobar="value1" xmlns:p="uri2"/>');
+}, 'Check if attribute serialization takes into account of following xmlns:* attributes');
+
+test(function() {
+  const input = '<root xmlns:p="uri1"><child/></root>';
+  const root = (new DOMParser()).parseFromString(input, 'text/xml').documentElement;
+  root.firstChild.setAttributeNS('uri2', 'p:foobar', 'v');
+  const xmlString = (new XMLSerializer()).serializeToString(root);
+  assert_equals(xmlString, '<root xmlns:p="uri1"><child xmlns:ns1="uri2" ns1:foobar="v"/></root>');
+}, 'Check if attribute serialization takes into account of the same prefix declared in an ancestor element');
+
 test(function() {
   const input = '<root><child1/><child2/></root>';
   const root = (new DOMParser()).parseFromString(input, 'text/xml').documentElement;