Dart: Merge message pipe query and read into one native call.

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
@@ skipping 57 matching lines @@
   }
 
   _run(int idx) {
     if (idx == _numActiveClients) {
       idx = 0;
     }
     if (_doEcho) {
       if (_warmup) {
         _echo(idx, "ping").then((_) => new Timer(kDelay, () => _run(idx + 1)));
       } else {
-        _tracedEcho(idx).then((_) => new Timer(kDelay, () => _run(idx + 1)));
+        _tracedEcho(idx, "ping")
+            .then((_) => new Timer(kDelay, () => _run(idx + 1)));
       }
     }
   }
 
-  Future _tracedEcho(int idx) {
+  Future _tracedEcho(int idx, String s) {
     int start = getTimeTicksNow();
-    return _echo(idx, "ping").then((_) {
+    return _echo(idx, s).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((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);
 }