Revert "Switch FE to use the libraries.json format."

pkg/front_end/example/incremental_reload/compiler_with_invalidation.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.
 
 /// A wrapper on top of the [IncrementalKernelGenerator] that tracks
 /// file modifications between subsequent compilation requests and only
 /// invalidates those files that appear to be modified.
 library front_end.example.incremental_reload.compiler_with_invalidation;
 
 import 'dart:io';
 import 'dart:async';
+import 'dart:convert' show JSON;
 
 import 'package:front_end/compiler_options.dart';
 import 'package:front_end/incremental_kernel_generator.dart';
 import 'package:front_end/src/incremental/file_byte_store.dart';
 import 'package:front_end/src/incremental/byte_store.dart';
 import 'package:kernel/ast.dart';
 import 'package:kernel/binary/limited_ast_to_binary.dart';
 
 /// Create an instance of an [IncrementalCompiler] to compile a program whose
 /// main entry point file is [entry]. This uses some default options
 /// for the location of the sdk and temporary folder to save intermediate
 /// results.
 // TODO(sigmund): make this example work outside of the SDK repo.
 Future<IncrementalCompiler> createIncrementalCompiler(String entry,
     {bool persistent: true}) {
   var entryUri = Uri.base.resolve(entry);
   var dartVm = Uri.base.resolve(Platform.resolvedExecutable);
   var sdkRoot = dartVm.resolve("patched_sdk/");
   var tmpDir = Directory.systemTemp.createTempSync('ikg_cache');
   var options = new CompilerOptions()
     ..sdkRoot = sdkRoot
     ..packagesFileUri = Uri.base.resolve('.packages')
     ..strongMode = false
+    ..dartLibraries = loadDartLibraries(sdkRoot)
     // Note: we do not report error on the console because the incremental
     // compiler is an ongoing background service that shouldn't polute stdout.
     // TODO(sigmund): do something with the errors.
     ..onError = (_) {}
     ..byteStore =
         persistent ? new FileByteStore(tmpDir.path) : new MemoryByteStore();
   return IncrementalCompiler.create(options, entryUri);
 }
 
+/// Reads the `libraries.json` file for an SDK to provide the location of the
+/// SDK files.
+// TODO(sigmund): this should be handled by package:front_end internally.
+Map<String, Uri> loadDartLibraries(Uri sdkRoot) {
+  var libraries = sdkRoot.resolve('lib/libraries.json');
+  var map =
+      JSON.decode(new File.fromUri(libraries).readAsStringSync())['libraries'];
+  var dartLibraries = <String, Uri>{};
+  map.forEach((k, v) => dartLibraries[k] = libraries.resolve(v));
+  return dartLibraries;
+}
+
 /// An incremental compiler that monitors file modifications on disk and
 /// invalidates only files that have been modified since the previous time the
 /// compiler was invoked.
 class IncrementalCompiler {
   /// Underlying incremental compiler implementation.
   IncrementalKernelGenerator _generator;
 
   /// Last modification for each tracked input file.
   Map<Uri, DateTime> lastModified = {};
 
@@ skipping 108 matching lines @@
     result.errorSeen = true;
   }
 
   result.changed = compiler.changed;
   result.totalFiles = compiler.lastModified.length;
   result.invalidateTime = compiler.invalidateTime;
   result.compileTime = compiler.compileTime;
   result.reloadTime = 0;
   return result;
 }