fix(benchpress): benchpress fixes and a smoke test for Dart

modules/examples/test/benchpress/webdriver_async.server.spec.dart

@@ -0,0 +1,58 @@
+import 'dart:async';
+import 'dart:io' show Platform;
+import 'package:guinness/guinness.dart';
+import 'package:benchpress/benchpress.dart';
+import 'package:benchpress/src/webdriver/async_webdriver_adapter.dart';
+import 'package:webdriver/webdriver.dart' show WebDriver, Capabilities, LogType, LogLevel, By;
+
+main() {
+  describe('benchpress', () {
+    WebDriver driver;
+    Runner runner;
+
+    beforeEach(() async {
+      driver = await createTestDriver();
+      await driver.get('http://localhost:8002/examples/src/benchpress/index.html');
+
+      var bindings = [
+        bind(WebDriverAdapter).toFactory(() => new AsyncWebDriverAdapter(driver), [])
+      ];
+      runner = new Runner(bindings);
+    });
+
+    afterEach(() async {
+      await driver.close();
+    });
+
+    it('should work', () {
+      return runner.sample(
+        id: 'benchpress smoke test',
+        execute: () async {
+          var button = await driver.findElement(const By.tagName('button'));
+          await button.click();
+          var logText = await (await driver.findElement(const By.id('log'))).text;
+          expect(logText, 'hi');
+        }
+      );
+    });
+  });
+}
+
+Future<WebDriver> createTestDriver() {
+  Map env = Platform.environment;
+  return WebDriver.createDriver(desiredCapabilities: {
+    'name': 'Dartium',
+    'browserName': 'chrome',
+    'chromeOptions': {
+      'binary': env['DARTIUM_BIN'],
+      'args': ['--js-flags=--expose-gc'],
+      'perfLoggingPrefs': {
+        'traceCategories': 'blink.console,disabled-by-default-devtools.timeline'
+      },
+    },
+    'loggingPrefs': {
+      'performance': 'ALL',
+      'browser': 'ALL',
+    }
+  });
+}