dart2js: fix crash when annotations have syntax errors (fix #23983)

pkg/compiler/lib/src/compile_time_constants.dart

Index: pkg/compiler/lib/src/compile_time_constants.dart
diff --git a/pkg/compiler/lib/src/compile_time_constants.dart b/pkg/compiler/lib/src/compile_time_constants.dart
index 4b0be2dd57e82be760717401281eaf4ed4efc4c2..f5ec1ee877f9109ef3a0c0cff7af4aa6d5ac6f84 100644
--- a/pkg/compiler/lib/src/compile_time_constants.dart
+++ b/pkg/compiler/lib/src/compile_time_constants.dart
@@ -336,6 +336,8 @@ class CompileTimeConstantEvaluator extends Visitor<AstConstant> {
   ConstantSystem get constantSystem => handler.constantSystem;
 
   AstConstant evaluate(Node node) {
+    // TODO(johnniwinter): should there be a visitErrorNode?

[Johnni Winther, 2015/07/27 07:57:05]

'johnniwinter' -> 'johnniwinther' (but kudos for getting 'johnni' right :)

[Siggi Cherem (dart-lang), 2015/07/27 16:26:44]

Oh thanks for letting me know :) 

I forgot to include it when I submitted (I got confused and thought it was
another CL), but I sent a follow up change to fix it.

+    if (node is ErrorNode) return new ErroneousAstConstant(context, node);
     return node.accept(this);
   }