W3C Test: Import web-platform-tests/html/semantics

LayoutTests/imported/web-platform-tests/html/semantics/embedded-content/the-img-element/srcset/common.js

+setup({explicit_done:true});
+
+function check(img) {
+  var name = format_value(img.getAttribute('srcset'));
+  if (img.hasAttribute('sizes')) {
+    name += ' sizes=' + format_value(img.getAttribute('sizes'));
+  }
+  if (img.hasAttribute('data-desc')) {
+    name += ' (' + img.getAttribute('data-desc') + ')';
+  }
+  test(function() {
+    var expect = img.dataset.expect;
+    if ('resolve' in img.dataset) {
+      var a = document.createElement('a');
+      a.href = expect;
+      expect = a.href;
+    }
+    assert_equals(img.currentSrc, expect);
+  }, name);
+}
+
+onload = function() {
+  [].forEach.call(document.images, check);
+  done();
+};