Add command-line parameter enabling assert messages.

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

Index: pkg/compiler/lib/src/scanner/class_element_parser.dart
diff --git a/pkg/compiler/lib/src/scanner/class_element_parser.dart b/pkg/compiler/lib/src/scanner/class_element_parser.dart
index 627b0add7e9bb1971aa9da411a31019f1a8d18da..23b38a96f7c79c3de77320ec0fd372b0c3ed04ee 100644
--- a/pkg/compiler/lib/src/scanner/class_element_parser.dart
+++ b/pkg/compiler/lib/src/scanner/class_element_parser.dart
@@ -5,7 +5,9 @@
 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);
 }
@@ -48,7 +50,8 @@ class PartialClassElement extends ClassElementX with PartialElement {
     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));