Add command-line parameter enabling assert messages.

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

Index: pkg/compiler/lib/src/scanner/parser.dart
diff --git a/pkg/compiler/lib/src/scanner/parser.dart b/pkg/compiler/lib/src/scanner/parser.dart
index 69d4e62feb4277ad9d4395c98865e910e1361327..77e6a181aa3e68b0bd7e5611f312f95132391bfa 100644
--- a/pkg/compiler/lib/src/scanner/parser.dart
+++ b/pkg/compiler/lib/src/scanner/parser.dart
@@ -43,9 +43,17 @@ class Parser {
   bool mayParseFunctionExpressions = true;
   bool yieldIsKeyword;
   bool awaitIsKeyword;
+  bool allowAssertMessage;
 
   Parser(this.listener,
-         {this.yieldIsKeyword: false, this.awaitIsKeyword: false});
+         {this.yieldIsKeyword: false,
+          this.awaitIsKeyword: false,
+          this.allowAssertMessage: false}) {
+    print("PARSER: $allowAssertMessage");
+    if (!allowAssertMessage) {
+      try {throw 0;} catch(e,s) {print(s);}
+    }
+  }
 
   Token parseUnit(Token token) {
     listener.beginCompilationUnit(token);