Support messages in assert().

lib/src/source_visitor.dart

Index: lib/src/source_visitor.dart
diff --git a/lib/src/source_visitor.dart b/lib/src/source_visitor.dart
index cbe34484186070983126c260092c860efab0f898..529e420a4eff3d0ec548a0a13bc72b4dc1577ca2 100644
--- a/lib/src/source_visitor.dart
+++ b/lib/src/source_visitor.dart
@@ -161,10 +161,13 @@ class SourceVisitor implements AstVisitor {
   visitAssertStatement(AssertStatement node) {
     _simpleStatement(node, () {
       token(node.assertKeyword);
-      token(node.leftParenthesis);
-      soloZeroSplit();
-      visit(node.condition);
-      token(node.rightParenthesis);
+
+      var arguments = [node.condition];
+      if (node.message != null) arguments.add(node.message);
+
+      var visitor = new ArgumentListVisitor.forArguments(
+          this, node.leftParenthesis, node.rightParenthesis, arguments);
+      visitor.visit();
     });
   }