Use `Function` as function type syntax.

pkg/compiler/lib/src/helpers/helpers.dart

Index: pkg/compiler/lib/src/helpers/helpers.dart
diff --git a/pkg/compiler/lib/src/helpers/helpers.dart b/pkg/compiler/lib/src/helpers/helpers.dart
index 14a788708236cd8b858d9f4cfd6f81b4f1160d6a..f316a57d116e13140754e28bd4bcf39162e4ccf0 100644
--- a/pkg/compiler/lib/src/helpers/helpers.dart
+++ b/pkg/compiler/lib/src/helpers/helpers.dart
@@ -37,29 +37,23 @@ class _DebugIndentation extends Indentation {
 
 _DebugIndentation _indentation = new _DebugIndentation();
 
-/// Function signature of [debugPrint].
-typedef DebugPrint(s);
-
 /// If [DEBUG_PRINT_ENABLED] is `true` print [s] using the current identation.
-DebugPrint get debugPrint {
+void Function(dynamic s) get debugPrint {
   enableDebugMode();
   // TODO(johnniwinther): Maybe disable debug mode after the call.
   return _debugPrint;
 }
 
 /// Implementation of [debugPrint].
-_debugPrint(s) {
+void _debugPrint(s) {
   if (DEBUG_PRINT_ENABLED) print('${_indentation.indentation}$s');
 }
 
-/// Function signature of [debugWrapPrint].
-typedef DebugWrapPrint(s, f());
-
 /// Wraps the call to [f] with a print of 'start:$s' and 'end:$s' incrementing
 /// the current indentation used by [debugPrint] during the execution of [f].
 ///
 /// Use this to get a tree-like debug printout for nested calls.
-DebugWrapPrint get debugWrapPrint {
+dynamic Function(dynamic s, dynamic Function() f) get debugWrapPrint {
   enableDebugMode();
   return _debugWrapPrint;
 }
@@ -82,7 +76,8 @@ typedef ReportHere(
     DiagnosticReporter reporter, Spannable node, String debugMessage);
 
 /// Print a message with a source location.
-ReportHere get reportHere {
+dynamic Function(DiagnosticReporter, Spannable node, String debugMessage)
+    get reportHere {
   enableDebugMode();
   return _reportHere;
 }