Add support for building patched_sdk and platform.dill for dart2js:

pkg/front_end/lib/src/fasta/kernel/body_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.body_builder;
 
 import '../fasta_codes.dart'
     show FastaMessage, codeExpectedButGot, codeExpectedFunctionBody;
 
 import '../parser/parser.dart' show FormalParameterType, optional;
@@ skipping 16 matching lines @@
 import 'package:kernel/clone.dart' show CloneVisitor;
 
 import 'package:kernel/transformations/flags.dart' show TransformerFlag;
 
 import 'package:kernel/class_hierarchy.dart' show ClassHierarchy;
 
 import 'package:kernel/core_types.dart' show CoreTypes;
 
 import 'frontend_accessors.dart' show buildIsNull, makeBinary, makeLet;
 
-import '../parser/dart_vm_native.dart' show skipNativeClause;
+import '../parser/dart2js_native.dart' show skipDart2jsNativeClause;
+
+import '../parser/dart_vm_native.dart' show skipVmNativeClause;
 
 import '../scanner/token.dart'
     show BeginGroupToken, Token, isBinaryOperator, isMinusOperator;
 
 import '../errors.dart' show formatUnexpected, internalError;
 
 import '../source/scope_listener.dart'
     show JumpTargetKind, NullValue, ScopeListener;
 
 import '../scope.dart' show ProblemBuilder;
@@ skipping 2438 matching lines @@
   @override
   void handleRecoverableError(Token token, FastaMessage message) {
     bool silent = hasParserError;
     super.handleRecoverableError(token, message);
     addCompileTimeError(message.charOffset, message.message, silent: silent);
   }
 
   @override
   Token handleUnrecoverableError(Token token, FastaMessage message) {
     if (isDartLibrary && message.code == codeExpectedFunctionBody) {
-      Token recover = skipNativeClause(token);
-      if (recover != null) return recover;
+      if (library.loader.target.forDart2js) {

[ahe, 2017/04/27 13:34:34]

Can we move this to a subclass of BodyBuilder?

[Siggi Cherem (dart-lang), 2017/04/28 21:37:20]

this moved to the target, which is easier to override once in package:compiler.
I still would like to get rid of the extra logic for this, so I added some TODOs
about it.

+        Token recover = skipDart2jsNativeClause(token);
+        if (recover != null) return recover;
+      } else {
+        Token recover = skipVmNativeClause(token);
+        if (recover != null) return recover;
+      }
     } else if (message.code == codeExpectedButGot) {
       String expected = message.arguments["string"];
       const List<String> trailing = const <String>[")", "}", ";", ","];
       if (trailing.contains(token.stringValue) && trailing.contains(expected)) {
         handleRecoverableError(token, message);
         return newSyntheticToken(token);
       }
     }
     return super.handleUnrecoverableError(token, message);
   }
@@ skipping 586 matching lines @@
   } else if (node is PrefixBuilder) {
     return node.name;
   } else if (node is ThisAccessor) {
     return node.isSuper ? "super" : "this";
   } else if (node is FastaAccessor) {
     return node.plainNameForRead;
   } else {
     return internalError("Unhandled: ${node.runtimeType}");
   }
 }