[DevTools] Migrate inspector-protocol/layers tests to new harness

third_party/WebKit/LayoutTests/inspector-protocol/layers/get-layers.js

+(async function(testRunner) {
+  let {page, session, dp} = await testRunner.startURL('../resources/get-layers.html', '');
+
+  function layerMutations(oldLayers, newLayers) {
+    var oldLayerIds = oldLayers.map(layer => layer.layerId);
+    var newLayerIds = newLayers.map(layer => layer.layerId);
+    return {
+      additions: newLayers.filter(layer => oldLayerIds.indexOf(layer.layerId) === -1),
+      removals: oldLayers.filter(layer => newLayerIds.indexOf(layer.layerId) === -1)
+    };
+  }
+
+  function attributesFromArray(attributes) {
+    var map = new Map();
+    for (var i = 0, count = attributes.length; i < count; i += 2)
+      map.set(attributes[i], attributes[i + 1]);
+    return map;
+  }
+
+  function dumpLayers(layers) {
+    function replacer(key, value) {
+      if (['layerId', 'parentLayerId', 'backendNodeId', 'paintCount'].indexOf(key) >= 0)
+        return typeof(value);
+      // some values differ based on port, but the ones we most
+      // care about will always be less or equal 100.
+      if ((key === 'width' || key === 'height') && value > 100)
+        return typeof(value);
+      return value;
+    }
+
+    // Keep 'internal' layers out for better stability.
+    layers = layers.filter(layer => !!layer.backendNodeId);
+    testRunner.log('\n' + JSON.stringify(layers, replacer, '    '));
+  }
+
+  await dp.DOM.getDocument();
+  dp.LayerTree.enable();
+  var initialLayers = (await dp.LayerTree.onceLayerTreeDidChange()).params.layers;
+
+  dp.Runtime.evaluate({expression: 'addCompositedLayer()'});
+  var modifiedLayers = (await dp.LayerTree.onceLayerTreeDidChange()).params.layers;
+
+  var mutations = layerMutations(initialLayers, modifiedLayers);
+  var newLayer = mutations.additions[0];
+
+  var nodeResponse = await dp.DOM.pushNodesByBackendIdsToFrontend({backendNodeIds: [newLayer.backendNodeId]});
+  var attributesResponse = await dp.DOM.getAttributes({nodeId: nodeResponse.result.nodeIds[0]});
+  var attributes = attributesFromArray(attributesResponse.result.attributes);
+  if (attributes.get('id') !== 'last-element')
+    testRunner.log('FAIL: Did not obtain the expected element for the last inserted layer.');
+
+  dumpLayers(initialLayers);
+  dumpLayers(modifiedLayers);
+  testRunner.log('DONE!');
+  testRunner.completeTest();
+})