Read SDK and patches from a JSON file.

pkg/front_end/lib/src/fasta/kernel/kernel_library_builder.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.kernel_library_builder;
 
 import 'package:front_end/src/scanner/token.dart' show Token;
 
 import 'package:kernel/ast.dart';
 
@@ skipping 43 matching lines @@
         ProcedureBuilder,
         Scope,
         TypeBuilder,
         TypeVariableBuilder,
         compareProcedures;
 
 class KernelLibraryBuilder
     extends SourceLibraryBuilder<KernelTypeBuilder, Library> {
   final Library library;
 
+  final bool isPatch;
+
   final Map<String, SourceClassBuilder> mixinApplicationClasses =
       <String, SourceClassBuilder>{};
 
   final List<List> argumentsWithMissingDefaultValues = <List>[];
 
   final List<KernelProcedureBuilder> nativeMethods = <KernelProcedureBuilder>[];
 
   final List<KernelTypeVariableBuilder> boundlessTypeVariables =
       <KernelTypeVariableBuilder>[];
 
-  KernelLibraryBuilder(Uri uri, Uri fileUri, Loader loader)
+  KernelLibraryBuilder(Uri uri, Uri fileUri, Loader loader, this.isPatch)
       : library = new Library(uri, fileUri: relativizeUri(fileUri)),
         super(loader, fileUri);
 
   Library get target => library;
 
   Uri get uri => library.importUri;
 
   KernelTypeBuilder addNamedType(
       String name, List<KernelTypeBuilder> arguments, int charOffset) {
     return addType(
@@ skipping 758 matching lines @@
           mixinApplicationClasses.putIfAbsent(name, () => builder);
       if (existing != builder) {
         part.scope.local.remove(name);
       }
     });
     super.includePart(part);
     nativeMethods.addAll(part.nativeMethods);
     boundlessTypeVariables.addAll(part.boundlessTypeVariables);
   }
 }