[DevTools] Migrate inspector-protocol/{page,dom-snapshot} tests to new harness

third_party/WebKit/LayoutTests/inspector-protocol/dom-snapshot/dom-snapshot-getSnapshot.js

+(async function(testRunner) {
+  let {page, session, dp} = await testRunner.startURL('../resources/dom-snapshot.html', 'Tests DOMSnapshot.getSnapshot method.');
+
+  await session.evaluate(`
+    var host = document.querySelector('#shadow-host').createShadowRoot();
+    var template = document.querySelector('#shadow-template');
+    host.appendChild(template.content);
+    template.remove();
+    document.body.offsetWidth;
+  `);
+
+  function stabilize(key, value) {
+    var unstableKeys = ['documentURL', 'baseURL', 'frameId', 'backendNodeId'];
+    if (unstableKeys.indexOf(key) !== -1)
+      return '<' + typeof(value) + '>';
+    if (typeof value === 'string' && value.indexOf('/dom-snapshot/') !== -1)
+      value = '<value>';
+    return value;
+  }
+
+  var whitelist = ['transform', 'transform-origin', 'height', 'width', 'display', 'outline-color', 'color'];
+  var response = await dp.DOMSnapshot.getSnapshot({'computedStyleWhitelist': whitelist});
+  if (response.error)
+    testRunner.log(response);
+  else
+    testRunner.log(JSON.stringify(response.result, stabilize, 2));
+  testRunner.completeTest();
+})