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

third_party/WebKit/LayoutTests/inspector-protocol/resources/layer-protocol-test.js

-function initialize_layersTest()
-{
-
-var layers;
-var layerTreeChangeCallback;
-
-InspectorTest.step = function(test)
-{
-    InspectorTest.sendCommand(test.command, test.parameters, function(messageObject) {
-        if (messageObject.hasOwnProperty("error")) {
-            InspectorTest.log("FAIL: " + messageObject.error.message + " (" + messageObject.error.code + ")");
-            InspectorTest.completeTest();
-            return;
-        }
-        if (test.callback)
-            test.callback(messageObject.result);
-    });
-};
-
-function onLayerTreeChanged(message)
-{
-    layers = message.params.layers;
-    if (layerTreeChangeCallback) {
-        var callback = layerTreeChangeCallback;
-        layerTreeChangeCallback = null;
-        callback(layers);
-    }
-}
-
-InspectorTest.setLayerTreeChangeCallback = function(callback)
-{
-    layerTreeChangeCallback = callback;
-}
-
-InspectorTest.enableLayerTreeAgent = function(callback)
-{
-    if (layers) {
-        callback(layers);
-        return;
-    }
-    InspectorTest.eventHandler["LayerTree.layerTreeDidChange"] = onLayerTreeChanged;
-    InspectorTest.setLayerTreeChangeCallback(callback);
-    InspectorTest.sendCommand("DOM.getDocument", {}, function() {
-        InspectorTest.sendCommand("LayerTree.enable", {}, function() { });
-    });
-}
-
-}