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

pkg/front_end/example/incremental_reload/compiler_with_invalidation.dart

Index: pkg/front_end/example/incremental_reload/compiler_with_invalidation.dart
diff --git a/pkg/front_end/example/incremental_reload/compiler_with_invalidation.dart b/pkg/front_end/example/incremental_reload/compiler_with_invalidation.dart
index 061771c9e54ce775f8b32280931105da699801f4..c5d976027032fa73ea36adf4878edf736f423ab4 100644
--- a/pkg/front_end/example/incremental_reload/compiler_with_invalidation.dart
+++ b/pkg/front_end/example/incremental_reload/compiler_with_invalidation.dart
@@ -9,6 +9,7 @@ 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';
@@ -32,6 +33,7 @@ Future<IncrementalCompiler> createIncrementalCompiler(String entry,
     ..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.
@@ -41,6 +43,18 @@ Future<IncrementalCompiler> createIncrementalCompiler(String entry,
   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.