Repeats and fixes the changes landed & reverted as CL 1789553003.

pkg/compiler/lib/src/parser/parser.dart

 // Copyright (c) 2012, 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 dart2js.parser;
 
+import '../options.dart' show
+    ParserOptions;
 import '../common.dart';
 import '../tokens/keyword.dart' show
     Keyword;
 import '../tokens/precedence.dart' show
     PrecedenceInfo;
 import '../tokens/precedence_constants.dart' show
     AS_INFO,
     ASSIGNMENT_PRECEDENCE,
     CASCADE_PRECEDENCE,
     EQUALITY_PRECEDENCE,
@@ skipping 73 matching lines @@
  * events (except for errors) and may return null.
  *
  * Parse methods are generally named parseGrammarProductionSuffix. The
  * suffix can be one of "opt", or "star". "opt" means zero or one
  * matches, "star" means zero or more matches. For example,
  * [parseMetadataStar] corresponds to this grammar snippet: [:
  * metadata* :], and [parseTypeOpt] corresponds to: [: type? :].
  */
 class Parser {
   final Listener listener;
+  final ParserOptions parserOptions;
   bool mayParseFunctionExpressions = true;
-  final bool enableConditionalDirectives;
   bool asyncAwaitKeywordsEnabled;
 
-  Parser(this.listener,
-      {this.enableConditionalDirectives: false,
-       this.asyncAwaitKeywordsEnabled: false});
+  Parser(this.listener, this.parserOptions,
+      {this.asyncAwaitKeywordsEnabled: false});
 
   Token parseUnit(Token token) {
     listener.beginCompilationUnit(token);
     int count = 0;
     while (!identical(token.kind, EOF_TOKEN)) {
       token = parseTopLevelDeclaration(token);
       listener.endTopLevelDeclaration(token);
       count++;
     }
     listener.endCompilationUnit(count, token);
@@ skipping 56 matching lines @@
     Token semicolon = token;
     token = expect(';', token);
     listener.endImport(importKeyword, deferredKeyword, asKeyword, semicolon);
     return token;
   }
 
   /// if (test) uri
   Token parseConditionalUris(Token token) {
     listener.beginConditionalUris(token);
     int count = 0;
-    if (enableConditionalDirectives) {
+    if (parserOptions.enableConditionalDirectives) {
       while (optional('if', token)) {
         count++;
         token = parseConditionalUri(token);
       }
     }
     listener.endConditionalUris(count);
     return token;
   }
 
   Token parseConditionalUri(Token token) {
@@ skipping 2584 matching lines @@
     }
     listener.handleContinueStatement(hasTarget, continueKeyword, token);
     return expectSemicolon(token);
   }
 
   Token parseEmptyStatement(Token token) {
     listener.handleEmptyStatement(token);
     return expectSemicolon(token);
   }
 }