Move the dom directory from web-platform-tests/ to wpt/.

third_party/WebKit/LayoutTests/imported/wpt/dom/nodes/mutationobservers.js

 // Compares a mutation record to a predefined one
 // mutationToCheck is a mutation record from the user agent
 // expectedRecord is a mutation record minted by the test
 //    for expectedRecord, if properties are ommitted, they get default ones
 function checkRecords(target, mutationToCheck, expectedRecord) {
   var mr1;
   var mr2;
 
 
   function checkField(property, isArray) {
@@ skipping 56 matching lines @@
   }
 
   test.step(
     function () {
       (new MutationObserver(moc)).observe(node, mutationObserverOptions);
       mutationFunction();
     }
   );
   return mutationRecordSequence.length
 }