Use `Function` as function type syntax.

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

Index: pkg/compiler/lib/src/helpers/trace.dart
diff --git a/pkg/compiler/lib/src/helpers/trace.dart b/pkg/compiler/lib/src/helpers/trace.dart
index 021ba97fd92e01bb96972ed913243e42df47960d..389f5c8c9ecd3c51b851b4bee2f01adfdc850b7e 100644
--- a/pkg/compiler/lib/src/helpers/trace.dart
+++ b/pkg/compiler/lib/src/helpers/trace.dart
@@ -5,10 +5,6 @@
 import '../common.dart';
 import '../util/util.dart';
 
-/// Function signature for [trace].
-typedef void Trace(String message,
-    {bool condition(String stackTrace), int limit, bool throwOnPrint});
-
 /**
  * Helper method for printing stack traces for debugging.
  *
@@ -26,13 +22,16 @@ typedef void Trace(String message,
  * unknown call-sites in tests by filtering known call-sites and throwning
  * otherwise.
  */
-Trace get trace {
+void Function(String message, {bool Function(String stackTrace) condition, int limit,
+    bool throwOnPrint})
+get trace {
   enableDebugMode();
   return _trace;
 }
 
 void _trace(String message,
-    {bool condition(String stackTrace), int limit, bool throwOnPrint: false}) {
+    {bool Function(String stackTrace) condition, int limit,
+    bool throwOnPrint: false}) {
   try {
     throw '';
   } catch (e, s) {
@@ -59,9 +58,10 @@ traceExceptions(List<String> exceptions) {
 }
 
 /// Function signature of [traceAndReport].
-typedef void TraceAndReport(
-    DiagnosticReporter reporter, Spannable node, String message,
-    {bool condition(String stackTrace), int limit, bool throwOnPrint});
+typedef TraceAndReport = void Function(
+    DiagnosticReporter, Spannable node, String message,
+    {bool Function(String stackTrace) condition, int limit, bool throwOnPrint})
+
 
 /// Calls [reportHere] and [trace] with the same message.
 TraceAndReport get traceAndReport {
@@ -75,7 +75,8 @@ TraceAndReport get reportAndTrace => traceAndReport;
 /// Implementation of [traceAndReport].
 void _traceAndReport(
     DiagnosticReporter reporter, Spannable node, String message,
-    {bool condition(String stackTrace), int limit, bool throwOnPrint: false}) {
+    {bool Function(String stackTrace) condition, int limit,
+    bool throwOnPrint: false}) {
   trace(message, limit: limit, throwOnPrint: throwOnPrint,
       condition: (String stackTrace) {
     bool result = condition != null ? condition(stackTrace) : true;