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

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

Index: pkg/front_end/lib/src/fasta/target_implementation.dart
diff --git a/pkg/front_end/lib/src/fasta/target_implementation.dart b/pkg/front_end/lib/src/fasta/target_implementation.dart
index 142f1c70a7d147e4263ae3fb5bd0a15fbd42ce35..d702e6e7473b41879e437a776ef016c0f0500046 100644
--- a/pkg/front_end/lib/src/fasta/target_implementation.dart
+++ b/pkg/front_end/lib/src/fasta/target_implementation.dart
@@ -8,14 +8,8 @@ import 'package:kernel/target/vm.dart' show VmTarget;
 
 import 'builder/builder.dart' show Builder, ClassBuilder, LibraryBuilder;
 
-import 'parser/dart_vm_native.dart' as vm show skipNativeClause;
-
-import 'scanner/token.dart' show Token;
-
 import 'loader.dart' show Loader;
 
-import 'quote.dart' show unescapeString;
-
 import 'target.dart' show Target;
 
 import 'ticker.dart' show Ticker;
@@ -84,11 +78,6 @@ abstract class TargetImplementation extends Target {
     }
   }
 
-  Token skipNativeClause(Token token) => vm.skipNativeClause(token);
-
-  String extractNativeMethodName(Token token) =>
-      unescapeString(token.next.lexeme);
-
   void addSourceInformation(
       Uri uri, List<int> lineStarts, List<int> sourceCode);
 }