dart2js: add an example script that shows the distribution of code among

pkg/compiler/tool/library_size_split.dart

Index: pkg/compiler/tool/library_size_split.dart
diff --git a/pkg/compiler/tool/library_size_split.dart b/pkg/compiler/tool/library_size_split.dart
new file mode 100644
index 0000000000000000000000000000000000000000..dcfaefeb22ae21b1a4efe5cf69e940ee8cfc02f0
--- /dev/null
+++ b/pkg/compiler/tool/library_size_split.dart
@@ -0,0 +1,132 @@
+// Copyright (c) 2015, 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.
+
+/// Command-line tool to show the size distribution of generated code among
+/// libraries. Libraries can be grouped using regular expressions. See
+/// [defaultGrouping] for an example.
+library compiler.tool.library_size_split;
+
+import 'dart:convert';
+import 'dart:io';
+import 'dart:math' show max;
+
+import 'package:compiler/src/info/info.dart';
+import 'package:yaml/yaml.dart';
+
+main(args) {
+  if (args.length < 1) {
+    print('usage: dart tool/library_size_split.dart '
+        'path-to-info.json [grouping.yaml]');
+    exit(1);
+  }
+
+  var filename = args[0];
+  var json = JSON.decode(new File(filename).readAsStringSync());
+  var info = AllInfo.parseFromJson(json);
+
+  var groupingText = args.length > 1
+      ? new File(args[1]).readAsStringSync() : defaultGrouping;
+  var groupingYaml = loadYaml(groupingText);
+  var groups = [];
+  for (var group in groupingYaml['groups']) {
+    groups.add(new _Group(group['name'],
+        new RegExp(group['regexp']),
+        group['cluster'] ?? 0));
+  }
+
+  var sizes = {};
+  for (LibraryInfo lib in info.libraries) {
+    groups.forEach((group) {
+      var match = group.matcher.firstMatch('${lib.uri}');
+      if (match != null) {
+        var name = group.name;
+        if (name == null && match.groupCount > 0) name = match.group(1);
+        if (name == null) name = match.group(0);
+        sizes.putIfAbsent(name, () => new _SizeEntry(name, group.cluster));
+        sizes[name].size += lib.size;
+      }
+    });
+  }
+
+  var all = sizes.keys.toList();
+  all.sort((a, b) => sizes[a].compareTo(sizes[b]));
+  var realTotal = info.program.size;
+  var longest = all.fold(0, (count, value) => max(count, value.length));
+  longest = max(longest, 'Program Size'.length);
+  var lastCluster = 0;
+  for (var name in all) {
+    var entry = sizes[name];
+    if (lastCluster < entry.cluster) {
+      print(' ' + ('-' * (longest + 18)));
+      lastCluster = entry.cluster;
+    }
+    var size = entry.size;
+    var percent = (size * 100 / realTotal).toStringAsFixed(2);
+    print(' ${_pad(name, longest + 1, right: true)}'
+          ' ${_pad(size, 8)} ${_pad(percent, 6)}%');
+  }
+  print(' ${_pad("Program Size", longest + 1, right: true)}'
+      ' ${_pad(realTotal, 8)} ${_pad(100, 6)}%');
+}
+
+/// A group defined in the configuration.
+class _Group {
+  /// Name of the group. May be null if the name is derived from the matcher. In
+  /// that case, the name would be group(1) of the matched expression if it
+  /// exist, or group(0) otherwise.
+  final String name;
+
+  /// Regular expression matching members of the group.
+  final RegExp matcher;
+
+  /// Index used to cluster groups together. Useful when the grouping
+  /// configuration describes some coarser groups than orders (e.g. summary of
+  /// packages would be in a different cluster than a summary of libraries).
+  final int cluster;
+
+  _Group(this.name, this.matcher, this.cluster);
+}
+
+class _SizeEntry {
+  final String name;
+  final int cluster;
+  int size = 0;
+
+  _SizeEntry(this.name, this.cluster);
+
+  int compareTo(_SizeEntry other) =>
+      cluster == other.cluster ? size - other.size : cluster - other.cluster;
+}
+
+_pad(value, n, {bool right: false}) {
+  var s = '$value';
+  if (s.length >= n) return s;
+  var pad = ' ' * (n - s.length);
+  return right ? '$s$pad' : '$pad$s';
+}
+
+/// Example grouping specification: a yaml format containing a list of
+/// group specifications. A group is specified by 3 parameters:
+///    - name: the name that will be shown in the table of results
+///    - regexp: a regexp used to match entries that belong to the group
+///    - cluster: a clustering index, the higher the value, the later it will be
+///    shown in the results.
+/// Both cluster and name are optional. If cluster is omitted, the default value
+/// is 0. If the name is omitted, it is extracted from the regexp, either as
+/// group(1) if it is available or group(0) otherwise.
+final defaultGrouping = """
+groups:
+- { name: "Total (excludes preambles, statics & consts)", regexp: ".*", cluster: 3}
+- { name: "Loose files", regexp: "file://.*", cluster: 2}
+- { name: "All packages", regexp: "package:.*", cluster: 2}
+- { name: "Core libs", regexp: "dart:.*", cluster: 2}
+# We omitted `name` to extract the group name from the regexp directly.
+# Here the name is the name of the package:
+- { regexp: "package:([^/]*)", cluster: 1}
+# Here the name is the url of the package and dart core libraries:
+- { regexp: "package:.*"}
+- { regexp: "dart:.*"}
+# Here the name is the relative path of loose files:
+- { regexp: "file://${Directory.current.path}/(.*)" }
+""";