Add metrics example

Author: kklisura

cdt-examples/src/main/java/com/github/kklisura/cdt/examples/PerformanceMetricsExample.java

@@ -0,0 +1,62 @@
+package com.github.kklisura.cdt.examples;
+
+import com.github.kklisura.cdt.launch.ChromeLauncher;
+import com.github.kklisura.cdt.protocol.commands.Network;
+import com.github.kklisura.cdt.protocol.commands.Page;
+import com.github.kklisura.cdt.protocol.commands.Performance;
+import com.github.kklisura.cdt.protocol.types.performance.Metric;
+import com.github.kklisura.cdt.services.ChromeDevToolsService;
+import com.github.kklisura.cdt.services.ChromeService;
+import com.github.kklisura.cdt.services.types.ChromeTab;
+
+import java.util.List;
+
+/**
+ * Metric example
+ *
+ * @author Kenan Klisura
+ */
+public class PerformanceMetricsExample {
+  public static void main(String[] args) {
+    // Create chrome launcher.
+    final ChromeLauncher launcher = new ChromeLauncher();
+
+    // Launch chrome either as headless (true) or regular (false).
+    final ChromeService chromeService = launcher.launch(false);
+
+    // Create empty tab ie about:blank.
+    final ChromeTab tab = chromeService.createTab();
+
+    // Get DevTools service to this tab
+    final ChromeDevToolsService devToolsService = chromeService.createDevToolsService(tab);
+
+    // Get individual commands
+    final Page page = devToolsService.getPage();
+    final Network network = devToolsService.getNetwork();
+    final Performance performance = devToolsService.getPerformance();
+
+    performance.enable();
+    network.onLoadingFinished(
+        event -> {
+          // Close the tab and close the browser when loading finishes.
+          List<Metric> metrics = performance.getMetrics();
+          try {
+            for (Metric metric : metrics) {
+              System.out.println(metric.getName() + ": " + metric.getValue());
+            }
+          } catch (Exception e) {
+            System.out.println(e.getMessage());
+          }
+          chromeService.closeTab(tab);
+          launcher.close();
+        });
+
+    // Enable network events.
+    network.enable();
+
+    // Navigate to github.com.
+    page.navigate("https://www.github.com");
+
+    devToolsService.waitUntilClosed();
+  }
+}