Add command-line parameter enabling assert messages.

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

 // Copyright (c) 2011, 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 scanner;
 
 class ClassElementParser extends PartialParser {
-  ClassElementParser(Listener listener) : super(listener);
+  ClassElementParser(Listener listener,
+                     {bool allowAssertMessage: false})
+      : super(listener, allowAssertMessage: allowAssertMessage);
 
   Token parseClassBody(Token token) => fullParseClassBody(token);
 }
 
 class PartialClassElement extends ClassElementX with PartialElement {
   ClassNode cachedNode;
 
   PartialClassElement(String name,
                       Token beginToken,
                       Token endToken,
@@ skipping 22 matching lines @@
     assert(invariant(this, cachedNode != null,
         message: "Node has not been computed for $this."));
     return cachedNode;
   }
 
   ClassNode parseNode(Compiler compiler) {
     if (cachedNode != null) return cachedNode;
     compiler.withCurrentElement(this, () {
       compiler.parser.measure(() {
         MemberListener listener = new MemberListener(compiler, this);
-        Parser parser = new ClassElementParser(listener);
+        Parser parser = new ClassElementParser(listener,
+            allowAssertMessage: compiler.allowAssertMessage);
         try {
           Token token = parser.parseTopLevelDeclaration(beginToken);
           assert(identical(token, endToken.next));
           cachedNode = listener.popNode();
           assert(
               invariant(
                   beginToken, listener.nodes.isEmpty,
                   message: "Non-empty listener stack: ${listener.nodes}"));
         } on ParserError {
           // TODO(ahe): Often, a ParserError is thrown while parsing the class
@@ skipping 173 matching lines @@
 
   void endMetadata(Token beginToken, Token periodBeforeName, Token endToken) {
     popNode(); // Discard arguments.
     if (periodBeforeName != null) {
       popNode(); // Discard name.
     }
     popNode(); // Discard node (Send or Identifier).
     pushMetadata(new PartialMetadataAnnotation(beginToken, endToken));
   }
 }