dart2js: dump info about dependencies added by the enqueuer

pkg/compiler/lib/src/dump_info.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.
 
 library dump_info;
 
 import 'dart:convert'
     show HtmlEscape, JsonEncoder, StringConversionSink, ChunkedConversionSink;
 
 import 'elements/elements.dart';
@@ skipping 345 matching lines @@
    * function body
    */
   void elementUsesSelector(Element element, UniverseSelector selector) {
     if (compiler.dumpInfo) {
       selectorsFromElement
           .putIfAbsent(element, () => new Set<UniverseSelector>())
           .add(selector);
     }
   }
 
+  final Map<Element, List<Element>> _dependencies = {};
+  void registerDependency(Element source, Element target) {
+    _dependencies.putIfAbsent(source, () => new Set()).add(target);
+  }
+
   /**
    * Returns an iterable of [Selection]s that are used by
    * [element].  Each [Selection] contains an element that is
    * used and the selector that selected the element.
    */
   Iterable<Selection> getRetaining(Element element) {
     if (!selectorsFromElement.containsKey(element)) {
       return const <Selection>[];
     } else {
       return selectorsFromElement[element].expand((UniverseSelector selector) {
@@ skipping 109 matching lines @@
       FunctionInfo functionInfo = infoCollector._elementToInfo[element];
       if (functionInfo == null) continue;
       for (Element held in inlineMap[element]) {
         Info heldInfo = infoCollector._elementToInfo[held];
         if (heldInfo == null) continue;
         functionInfo.uses.add(new DependencyInfo(heldInfo, 'inlined'));
       }
     }
 
     AllInfo result = infoCollector.result;
+
+    for (Element element in _dependencies.keys) {
+      var a = infoCollector._elementToInfo[element];
+      if (a == null) continue;
+      result.deps[a] = _dependencies[element]
+        .map((o) => infoCollector._elementToInfo[o])
+        .where((o) => o != null)
+        .toList();
+    }
+
     result.deferredFiles = compiler.deferredLoadTask.computeDeferredMap();
     stopwatch.stop();
     result.program = new ProgramInfo(
         size: _programSize,
         dart2jsVersion: compiler.hasBuildId ? compiler.buildId : null,
         compilationMoment: new DateTime.now(),
         compilationDuration: compiler.totalCompileTime.elapsed,
         toJsonDuration: stopwatch.elapsedMilliseconds,
         dumpInfoDuration: this.timing,
         noSuchMethodEnabled: compiler.backend.enabledNoSuchMethod,
         minified: compiler.enableMinification);
 
     ChunkedConversionSink<Object> sink = encoder.startChunkedConversion(
         new StringConversionSink.fromStringSink(buffer));
     sink.add(result.toJson());
     compiler.reportInfo(NO_LOCATION_SPANNABLE, MessageKind.GENERIC, {
       'text': "View the dumped .info.json file at "
           "https://dart-lang.github.io/dump-info-visualizer"
     });
   }
 }