Fix more strong mode errors in analyzer

pkg/analyzer/benchmark/errors_in_all_libraries.dart

Index: pkg/analyzer/benchmark/errors_in_all_libraries.dart
diff --git a/pkg/analyzer/benchmark/errors_in_all_libraries.dart b/pkg/analyzer/benchmark/errors_in_all_libraries.dart
index f4281912f39bda03216409ff5faab34f645a9603..0d68c2f2302c25bfef426b1672c53bffd6306fdd 100644
--- a/pkg/analyzer/benchmark/errors_in_all_libraries.dart
+++ b/pkg/analyzer/benchmark/errors_in_all_libraries.dart
@@ -40,8 +40,9 @@ void main(List<String> args) {
       new PackageUriResolver([new JavaFile(packageRoot)])
     ]);
 
-    context.analysisOptions.strongMode = true;
-    context.analysisOptions.strongModeHints = true;
+    AnalysisOptionsImpl options = context.analysisOptions;
+    options.strongMode = true;
+    options.strongModeHints = true;
 
     var mainSource =
         new FileBasedSource(new JavaFile(p.fromUri(Platform.script)));