fix(benchpress): explicitly require navigation to finish before continuing

modules/angular2/src/test_lib/perf_util.es6

@@ -32,8 +32,8 @@ function runBenchmark(config) {
       });
     }
     var url = encodeURI(config.url + '?' + urlParams.join('&'));
-    browser.get(url);
-    return benchpressRunner.sample({
+    return browser.get(url).then(function() {
+      benchpressRunner.sample({
         id: config.id,
         execute: config.work,
         prepare: config.prepare,
@@ -43,6 +43,7 @@ function runBenchmark(config) {
         ]
       });
     });
+  });
 }
 
 function getScaleFactor(possibleScalings) {