Adds a couple more measures to the benchmarking app

examples/dart/mojo_rtt_benchmark/lib/main.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This Mojo app is a benchmark of Mojo/Dart IPC Round Trip Times.
 // It creates many proxies from a single isolate, and makes requests using those
 // proxies round-robin.
 // To run it, and the other RTT benchmarks:
 //
 // $ ./mojo/devtools/common/mojo_benchmark [--release] mojo/tools/data/rtt_benchmarks
 
 import 'dart:async';
 
 import 'package:args/args.dart' as args;
 import 'package:common/tracing_helper.dart';
 import 'package:mojo/application.dart';
 import 'package:mojo/bindings.dart';
 import 'package:mojo/core.dart';
 import 'package:mojom/mojo/examples/echo.mojom.dart';
 
 class EchoTracingApp extends Application {
-  static const Duration kWarmupDuration = const Duration(seconds: 1);
+  static const Duration kWarmupDuration = const Duration(seconds: 5);
   static const Duration kDelay = const Duration(microseconds: 50);
   TracingHelper _tracing;
   List<EchoProxy> _echoProxies;
   bool _doEcho;
   bool _warmup;
   int _numClients;
   int _numActiveClients;
 
   EchoTracingApp.fromHandle(MojoHandle handle) : super.fromHandle(handle) {
     onError = _errorHandler;
@@ skipping 52 matching lines @@
     return _echo(idx, "ping").then((_) {
       int end = getTimeTicksNow();
       _tracing.traceDuration("ping", "mojo_rtt_benchmark", start, end);
     });
   }
 
   Future _echo(int idx, String s) {
     return _echoProxies[idx]
         .ptr
         .echoString(s)
-        .catchError((_) => _errorHandler());
+        .catchError((e) => _errorHandler());
   }
 
   _errorHandler() {
     _doEcho = false;
     return Future.wait(_echoProxies.map((p) => p.close())).then((_) {
       assert(MojoHandle.reportLeakedHandles());
     });
   }
 }
 
 main(List args) {
   MojoHandle appHandle = new MojoHandle(args[0]);
   new EchoTracingApp.fromHandle(appHandle);
 }