Add support for assert statements with messages to the analyzer.

pkg/analyzer/lib/src/generated/incremental_resolver.dart

Index: pkg/analyzer/lib/src/generated/incremental_resolver.dart
diff --git a/pkg/analyzer/lib/src/generated/incremental_resolver.dart b/pkg/analyzer/lib/src/generated/incremental_resolver.dart
index ea1e0fa9442a639986ee3e485793c1881b2f6c98..0c3087b5403f01bfe561e2fb540e88b329a9b100 100644
--- a/pkg/analyzer/lib/src/generated/incremental_resolver.dart
+++ b/pkg/analyzer/lib/src/generated/incremental_resolver.dart
@@ -1480,7 +1480,8 @@ class PoorMansIncrementalResolver {
     try {
       Token token = _scan(code);
       RecordingErrorListener errorListener = new RecordingErrorListener();
-      Parser parser = new Parser(_unitSource, errorListener);
+      Parser parser = new Parser(_unitSource, errorListener,
+          enableAssertMessage: _options.enableAssertMessage);
       AnalysisOptions options = _unitElement.context.analysisOptions;
       parser.parseGenericMethods = options.enableGenericMethods;
       CompilationUnit unit = parser.parseCompilationUnit(token);