Add LimitedBinaryPrinter, tests and switch incremental generator to it.

pkg/front_end/lib/src/incremental/limited_ast_to_binary.dart

+// Copyright (c) 2017, 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.
+
+import 'package:kernel/ast.dart';
+import 'package:kernel/binary/ast_to_binary.dart';
+
+/// Writes libraries that satisfy the [predicate].
+///
+/// Only the referenced subset of canonical names is indexed and written,
+/// so we don't waste time indexing all libraries of a program, when only
+/// a tiny subset is used.
+class LimitedBinaryPrinter extends BinaryPrinter {
+  final LibraryFilter predicate;
+
+  LimitedBinaryPrinter(Sink<List<int>> sink, this.predicate)
+      : super(sink, stringIndexer: new ReferencesStringIndexer());
+
+  @override
+  void addCanonicalNamesForLinkTable(List<CanonicalName> list) {
+    var stringIndexer = this.stringIndexer as ReferencesStringIndexer;

[Siggi Cherem (dart-lang), 2017/05/23 20:54:51]

nit: I've seen this style in fasta so far to use an assignment like:

ReferencesStringIndexer stringIndexer = this.stringIndexer;

instead of a cast.

It implies an implicit cast in strong-mode, but in spec-mode the cast will only
exist in checked-mode. this wont matter in the long run, but for now it doesn't
hurt.

[scheglov, 2017/05/23 21:54:43]

Done.

+    stringIndexer.referencedNames.forEach((name) {
+      if (name.index != -1) return;
+      name.index = list.length;
+      list.add(name);
+    });
+  }
+
+  @override
+  void buildStringIndex(Program program) {
+    program.libraries.where(predicate).forEach((library) {
+      stringIndexer.scanLibrary(library);
+    });
+    stringIndexer.finish();
+  }
+
+  @override
+  bool shouldWriteLibraryCanonicalNames(Library library) {
+    return predicate(library);
+  }
+
+  @override
+  void writeLibraries(Program program) {
+    var librariesToWrite = program.libraries.where(predicate).toList();
+    writeList(librariesToWrite, writeNode);
+  }
+
+  @override
+  void writeNode(Node node) {
+    if (node is Library && !predicate(node)) return;
+    node.accept(this);
+  }
+}
+
+/// Extension of [StringIndexer] that also indexes canonical names of
+/// referenced classes and members.
+class ReferencesStringIndexer extends StringIndexer {
+  final List<CanonicalName> referencedNames = <CanonicalName>[];
+
+  defaultMemberReference(Member node) {
+    _handleReferencedName(node.canonicalName);
+  }
+
+  visitClassReference(Class node) {
+    _handleReferencedName(node.canonicalName);
+  }
+
+  void _handleReferencedName(CanonicalName name) {
+    if (name == null || name.parent == null) return;
+    _handleReferencedName(name.parent);
+    referencedNames.add(name);
+    name.index = -1;
+    put(name.name);
+  }
+}