Prepare for development branch by updating externally-used API.

pkg/front_end/lib/src/fasta/target_implementation.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.target_implementation;
 
 import 'package:kernel/target/targets.dart' as backend show Target;
 
 import 'builder/builder.dart' show Builder, ClassBuilder, LibraryBuilder;
 
@@ skipping 60 matching lines @@
     }
     return cachedAbstractClassInstantiationError =
         loader.coreLibrary.getConstructor("AbstractClassInstantiationError");
   }
 
   /// Returns a reference to the constructor used for creating `native`
   /// annotations. The constructor is expected to accept a single argument of
   /// type String, which is the name of the native method.
   Builder getNativeAnnotation(Loader loader) {
     if (cachedNativeAnnotation != null) return cachedNativeAnnotation;
-    LibraryBuilder internal = loader.read(Uri.parse("dart:_internal"));
+    LibraryBuilder internal = loader.read(Uri.parse("dart:_internal"), -1);
     return cachedNativeAnnotation = internal.getConstructor("ExternalName");
   }
 
   void loadExtraRequiredLibraries(Loader loader) {
     for (String uri in backendTarget.extraRequiredLibraries) {
-      loader.read(Uri.parse(uri));
+      loader.read(Uri.parse(uri), -1);
     }
   }
 
   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);
 }