Revert "Move dart2js from sdk/lib/_internal/compiler to pkg/compiler"

pkg/compiler/lib/src/native/scanner.dart

-// Copyright (c) 2014, 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.
-
-part of native;
-
-void checkAllowedLibrary(ElementListener listener, Token token) {
-  LibraryElement currentLibrary = listener.compilationUnitElement.library;
-  if (!currentLibrary.canUseNative) {
-    listener.recoverableError(token, "Unexpected token");
-  }
-}
-
-Token handleNativeBlockToSkip(Listener listener, Token token) {
-  checkAllowedLibrary(listener, token);
-  token = token.next;
-  if (identical(token.kind, STRING_TOKEN)) {
-    token = token.next;
-  }
-  if (identical(token.stringValue, '{')) {
-    BeginGroupToken beginGroupToken = token;
-    token = beginGroupToken.endGroup;
-  }
-  return token;
-}
-
-Token handleNativeFunctionBody(ElementListener listener, Token token) {
-  checkAllowedLibrary(listener, token);
-  Token begin = token;
-  listener.beginReturnStatement(token);
-  token = token.next;
-  bool hasExpression = false;
-  if (identical(token.kind, STRING_TOKEN)) {
-    hasExpression = true;
-    listener.beginLiteralString(token);
-    listener.endLiteralString(0);
-    token = token.next;
-  }
-  listener.endReturnStatement(hasExpression, begin, token);
-  // TODO(ngeoffray): expect a ';'.
-  // Currently there are method with both native marker and Dart body.
-  return token.next;
-}