Add defer-layout tool.

bin/deferred_library_layout.dart

Index: bin/deferred_library_layout.dart
diff --git a/bin/deferred_library_layout.dart b/bin/deferred_library_layout.dart
new file mode 100644
index 0000000000000000000000000000000000000000..09caeb1578c6268d0ff27eed266464035e003aaa
--- /dev/null
+++ b/bin/deferred_library_layout.dart
@@ -0,0 +1,62 @@
+// Copyright (c) 2016, 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.
+
+/// This tool reports how code is divided among deferred chunks.
+library dart2js_info.bin.deferred_library_size;
+
+import 'dart:io';
+import 'package:dart2js_info/info.dart';
+import 'package:dart2js_info/src/util.dart';
+
+main(args) async {
+  AllInfo info = await infoFromFile(args.first);
+
+  Map<OutputUnitInfo, Map<LibraryInfo, List<BasicInfo>>> hunkMembers = {};
+  Map<LibraryInfo, Set<OutputUnitInfo>> libToHunks = {};
+  void register(BasicInfo info) {
+    var unit = info.outputUnit;
+    var lib = _libOf(info);
+    if (lib == null) return;
+    libToHunks.putIfAbsent(lib, () => new Set()).add(unit);
+    hunkMembers.putIfAbsent(unit, () => {})
+      .putIfAbsent(lib, () => []).add(info);
+  }
+
+  info.functions.forEach(register);
+  info.classes.forEach(register);
+  info.fields.forEach(register);
+  info.closures.forEach(register);
+
+  var dir = Directory.current.path;
+  hunkMembers.forEach((unit, map) {
+    print('Output unit ${unit.name ?? "main"}:');
+    if (unit.name == null || unit.name == 'main')  {
+      print('  loaded by default');
+    } else {
+      print('  loaded by importing: ${unit.imports}');
+    }
+
+    print('  contains:');
+    map.forEach((lib, elements) {
+      var uri = lib.uri;
+      var shortUri = (uri.scheme == 'file' && uri.path.startsWith(dir))
+          ? uri.path.substring(dir.length + 1)
+          : '$uri';
+
+      // If the entire library is in one chunk, just report the library name
+      // otherwise report which functions are on this chunk.
+      if (libToHunks[lib].length == 1) {
+        print('     - $shortUri');
+      } else {
+        print('     - $shortUri:');
+        for (var e in elements) {
+          print('       - ${kindToString(e.kind)} ${e.name}');
+        }
+      }
+    });
+    print('');
+  });
+}
+
+_libOf(e) => e is LibraryInfo || e == null ? e : _libOf(e.parent);