Rework DillLoader to allow adding multiple dills.

pkg/front_end/lib/src/fasta/dill/dill_loader.dart

Index: pkg/front_end/lib/src/fasta/dill/dill_loader.dart
diff --git a/pkg/front_end/lib/src/fasta/dill/dill_loader.dart b/pkg/front_end/lib/src/fasta/dill/dill_loader.dart
index 281bfff376555d777d16df7d9cac507525a78ded..1b843c94b32eef8ee9207d59f7675b99755f235c 100644
--- a/pkg/front_end/lib/src/fasta/dill/dill_loader.dart
+++ b/pkg/front_end/lib/src/fasta/dill/dill_loader.dart
@@ -6,47 +6,39 @@ library fasta.dill_loader;
 
 import 'dart:async' show Future;
 
-import 'dart:io' show File;
-
-import 'package:kernel/kernel.dart' show loadProgramFromBinary;
-
 import 'package:kernel/ast.dart' show Library, Program;
 
 import '../loader.dart' show Loader;
-
 import '../target_implementation.dart' show TargetImplementation;
-
 import 'dill_library_builder.dart' show DillLibraryBuilder;
 
 class DillLoader extends Loader<Library> {
-  Uri input;
-
   Program program;
 
   DillLoader(TargetImplementation target) : super(target);
 
-  DillLibraryBuilder read(Uri uri, [Uri fileUri]) => super.read(uri, fileUri);
-
-  Future<Null> buildOutline(DillLibraryBuilder builder) async {
-    if (program == null) {
-      byteCount = await new File.fromUri(input).length();
-      setProgram(await loadProgramFromBinary(input.toFilePath()));
+  /// Append compiled libraries from the given [program]. If the [filter] is
+  /// provided, append only libraries whose [Uri] is accepted by the [filter].
+  void appendLibraries(Program program, [bool filter(Uri uri)]) {
+    this.program ??= new Program();
+    program.unbindCanonicalNames();
+    for (Library library in program.libraries) {
+      if (filter == null || filter(library.importUri)) {
+        this.program.libraries.add(library);
+        read(library.importUri).library = library;
+      }
     }
-    builder.library.classes.forEach(builder.addClass);
-    builder.library.procedures.forEach(builder.addMember);
-    builder.library.fields.forEach(builder.addMember);
   }
 
   Future<Null> buildBody(DillLibraryBuilder builder) {
     return buildOutline(builder);
   }
 
-  void setProgram(Program program) {
-    assert(input != null);
-    this.program = program;
-    program.unbindCanonicalNames();
-    for (Library library in program.libraries) {
-      read(library.importUri).library = library;
-    }
+  Future<Null> buildOutline(DillLibraryBuilder builder) async {

[ahe, 2017/05/19 09:15:03]

Please stop sorting methods by name, it produces unnecessary merge conflicts and
makes it harder to use "git blame".

[scheglov, 2017/05/19 16:03:25]

Conflicts will happen only once.
Hopefully not too hard to merge for this small file.

I find it much more consistent to sort everything than to rely on vague and
impossible to get explanation about ad hoc order. Again, help to reduce the
cognitive load - no need to think, just do as everywhere.

[ahe, 2017/05/22 09:01:37]

What you personally perceive as reducing cognitive load has exactly the opposite
effect on me. If you feel that we should change our coding style, you should
suggest that we do so, and get agreement.

FWIW, following up on a highly contentious thread about automated formatting
isn't a good way to make such a proposal and not a great way to establish
agreement.

+    builder.library.classes.forEach(builder.addClass);
+    builder.library.procedures.forEach(builder.addMember);
+    builder.library.fields.forEach(builder.addMember);
   }
+
+  DillLibraryBuilder read(Uri uri, [Uri fileUri]) => super.read(uri, fileUri);
 }