Add names to nested declaration to ease debugging.

pkg/front_end/lib/src/fasta/source/outline_builder.dart

Index: pkg/front_end/lib/src/fasta/source/outline_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/source/outline_builder.dart b/pkg/front_end/lib/src/fasta/source/outline_builder.dart
index 3e85c42fcb057e3111ff01260bca0b3a00e01376..2e2289915100c43b954895622a23a83960b1b220 100644
--- a/pkg/front_end/lib/src/fasta/source/outline_builder.dart
+++ b/pkg/front_end/lib/src/fasta/source/outline_builder.dart
@@ -607,7 +607,7 @@ class OutlineBuilder extends UnhandledListener {
 
   @override
   void beginFunctionTypeAlias(Token token) {
-    library.beginNestedDeclaration(null, hasMembers: false);
+    library.beginNestedDeclaration("#typedef", hasMembers: false);
     silenceParserErrors = false;
   }
 
@@ -725,7 +725,7 @@ class OutlineBuilder extends UnhandledListener {
 
   @override
   void beginFactoryMethod(Token token) {
-    library.beginNestedDeclaration(null, hasMembers: false);
+    library.beginNestedDeclaration("#factory_method", hasMembers: false);
   }
 
   @override