Pool future creation to ensure no more than 10 ops are in flight

pkg/polymer/lib/src/build/runner.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * Definitions used to run the polymer linter and deploy tools without using
  * pub serve or pub deploy.
  */
 library polymer.src.build.runner;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 
 import 'package:args/args.dart';
 import 'package:barback/barback.dart';
+import 'package:barback/src/utils.dart' show forEachPooledFuture;
 import 'package:path/path.dart' as path;
 import 'package:stack_trace/stack_trace.dart';
 import 'package:yaml/yaml.dart';
 
 
 /** Collects different parameters needed to configure and run barback. */
 class BarbackOptions {
   /** Phases of transformers to run. */
   final List<List<Transformer>> phases;
 
@@ skipping 177 matching lines @@
   });
 }
 
 Future _emitTransformedFiles(AssetSet assets, BarbackOptions options) {
   // Copy all the assets we transformed
   var futures = [];
   var currentPackage = options.currentPackage;
   var transformTests = options.transformTests;
   var outPackages = path.join(options.outDir, 'packages');
 
-  return Future.forEach(assets, (asset) {
+  return forEachPooledFuture(assets, (asset) {
     var id = asset.id;
     var dir = _firstDir(id.path);
     if (dir == null) return null;
 
     var filepath;
     if (dir == 'lib') {
       // Put lib files directly under the packages folder (e.g. 'lib/foo.dart'
       // will be emitted at out/packages/package_name/foo.dart).
       filepath = path.join(outPackages, id.package,
           _toSystemPath(id.path.substring(4)));
@@ skipping 41 matching lines @@
  * of every file that was not transformed by barback.
  */
 Future _emitPackagesDir(BarbackOptions options) {
   if (options.transformPolymerDependencies) return new Future.value(null);
   var outPackages = path.join(options.outDir, 'packages');
   _ensureDir(outPackages);
 
   // Copy all the files we didn't process
   var dirs = options.packageDirs;
 
-  return Future.forEach(_polymerPackageDependencies, (package) {
-    return Future.forEach(_listPackageDir(package, 'lib', options), (relpath) {
+  return forEachPooledFuture(_polymerPackageDependencies, (package) {
+    return forEachPooledFuture(_listPackageDir(package, 'lib', options), (relpath) {
       var inpath = path.join(dirs[package], relpath);
       var outpath = path.join(outPackages, package, relpath.substring(4));
       return _copyFile(inpath, outpath);
     });
   });
 }
 
 /** Ensure [dirpath] exists. */
 void _ensureDir(String dirpath) {
   new Directory(dirpath).createSync(recursive: true);
@@ skipping 13 matching lines @@
 Future _copyFile(String inpath, String outpath) {
   _ensureDir(path.dirname(outpath));
   return new File(inpath).openRead().pipe(new File(outpath).openWrite());
 }
 
 /** Write contents of an [asset] into a file at [filepath]. */
 Future _writeAsset(String filepath, Asset asset) {
   _ensureDir(path.dirname(filepath));
   return asset.read().pipe(new File(filepath).openWrite());
 }