Rework DillLoader to allow adding multiple dills.

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

 // 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.
 
 library fasta;
 
 import 'dart:async' show Future;
 
 import 'dart:convert' show JSON;
 
 import 'dart:io' show BytesBuilder, Directory, File, exitCode;
 
 import 'package:front_end/physical_file_system.dart';
 import 'package:kernel/binary/ast_to_binary.dart'
     show LibraryFilteringBinaryPrinter;
 
-import 'package:kernel/kernel.dart' show Program, Library;
+import 'package:kernel/kernel.dart' show Library, Program, loadProgramFromBytes;
 
 import 'package:kernel/target/targets.dart' show Target, TargetFlags, getTarget;
 
 import 'compiler_command_line.dart' show CompilerCommandLine;
 
 import 'compiler_context.dart' show CompilerContext;
 
 import 'errors.dart' show InputError, formatUnexpected, inputError, reportCrash;
 
 import 'kernel/kernel_target.dart' show KernelTarget;
@@ skipping 145 matching lines @@
       return new CompilationResult.error(
           formatUnexpected(patchedSdk, -1, "Patched sdk directory not found."));
     }
 
     Program program;
     try {
       TranslateUri uriTranslator =
           await TranslateUri.parse(PhysicalFileSystem.instance, null, packages);
       final Ticker ticker = new Ticker(isVerbose: verbose);
       final DillTarget dillTarget = new DillTarget(ticker, uriTranslator);
-      dillTarget.read(patchedSdk.resolve('platform.dill'));
+      _appendDillForUri(dillTarget, patchedSdk.resolve('platform.dill'));
       final KernelTarget kernelTarget = new KernelTarget(
           PhysicalFileSystem.instance, dillTarget, uriTranslator, strongMode);
       kernelTarget.read(fileName);
       await dillTarget.writeOutline(null);
       program = await kernelTarget.writeOutline(null);
       program = await kernelTarget.writeProgram(null);
       if (kernelTarget.errors.isNotEmpty) {
         return new CompilationResult.errors(kernelTarget.errors
             .map((err) => err.toString())
             .toList(growable: false));
@@ skipping 49 matching lines @@
   await CompilerCommandLine.withGlobalOptions("", [""],
       (CompilerContext c) async {
     c.options.options["--packages"] = packages;
     if (verbose) {
       c.options.options["--verbose"] = true;
     }
 
     TranslateUri uriTranslator = await TranslateUri.parse(
         c.fileSystem, c.options.sdk, c.options.packages);
     ticker.logMs("Read packages file");
-    DillTarget dillTarget = new DillTarget(ticker, uriTranslator)
-      ..read(platform);
+    DillTarget dillTarget = new DillTarget(ticker, uriTranslator);
+    _appendDillForUri(dillTarget, platform);
     KernelTarget kernelTarget = new KernelTarget(PhysicalFileSystem.instance,
         dillTarget, uriTranslator, false, c.uriToSource);
 
     kernelTarget.read(script);
     await dillTarget.writeOutline(null);
     await kernelTarget.loader.buildOutlines();
     await kernelTarget.writeDepsFile(output, depsFile,
         extraDependencies: extraDependencies);
   });
 }
 
+/// Load the [Program] from the given [uri] and append its libraries
+/// to the [dillTarget].
+void _appendDillForUri(DillTarget dillTarget, Uri uri) {
+  var bytes = new File.fromUri(uri).readAsBytesSync();
+  var platformProgram = loadProgramFromBytes(bytes);
+  dillTarget.loader.appendLibraries(platformProgram);
+}
+
 // TODO(ahe): https://github.com/dart-lang/sdk/issues/28316
 class ByteSink implements Sink<List<int>> {
   final BytesBuilder builder = new BytesBuilder();
 
   void add(List<int> data) {
     builder.add(data);
   }
 
   void close() {
     // Nothing to do.
   }
 }