Move computation of method flags into model.

tests/compiler/dart2js/analyze_unused_dart2js_test.dart

Index: tests/compiler/dart2js/analyze_unused_dart2js_test.dart
diff --git a/tests/compiler/dart2js/analyze_unused_dart2js_test.dart b/tests/compiler/dart2js/analyze_unused_dart2js_test.dart
index 47ae7292010ca996d534368973d7ec8b51c2004a..570b5284a22a5015c81954e3d0bd61ae1bdd6d4a 100644
--- a/tests/compiler/dart2js/analyze_unused_dart2js_test.dart
+++ b/tests/compiler/dart2js/analyze_unused_dart2js_test.dart
@@ -17,10 +17,6 @@ const Map<String, List<String>> WHITE_LIST = const {
   // Helper methods for debugging should never be called from production code:
   "lib/src/helpers/": const [" is never "],
 
-  // Hack to give try private access:
-  "lib/src/js_emitter/program_builder.dart": const [
-      "The method 'buildClassWithFieldsForTry' is never called"],
-
   // Node.asLiteralBool is never used.
   "lib/src/tree/nodes.dart": const [
       "The method 'asLiteralBool' is never called"],