Use `Function` as function type syntax.

pkg/compiler/lib/src/compiler.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library dart2js.compiler_base;
 
 import 'dart:async' show EventSink, Future;
 
 import '../compiler_new.dart' as api;
 import 'cache_strategy.dart' show CacheStrategy;
@@ skipping 62 matching lines @@
 import 'types/types.dart' show GlobalTypeInferenceTask;
 import 'types/masks.dart' show CommonMasks;
 import 'universe/selector.dart' show Selector;
 import 'universe/world_builder.dart'
     show ResolutionWorldBuilder, CodegenWorldBuilder;
 import 'universe/use.dart' show StaticUse;
 import 'universe/world_impact.dart' show ImpactStrategy, WorldImpact;
 import 'util/util.dart' show Link, Setlet;
 import 'world.dart' show ClosedWorld, ClosedWorldRefiner, OpenWorld, WorldImpl;
 
-typedef Backend MakeBackendFuncion(Compiler compiler);
+typedef MakeBackendFuncion = Backend Function(Compiler compiler);
 
-typedef CompilerDiagnosticReporter MakeReporterFunction(
-    Compiler compiler, CompilerOptions options);
+typedef MakeReporterFunction =
+    CompilerDiagnosticReporter Function(Compiler compiler, CompilerOptions options);
 
 abstract class Compiler implements LibraryLoaderListener {
   Measurer get measurer;
 
   final IdGenerator idGenerator = new IdGenerator();
   WorldImpl _world;
   Types types;
   _CompilerCoreTypes _coreTypes;
   CompilerDiagnosticReporter _reporter;
   _CompilerResolution _resolution;
@@ skipping 2159 matching lines @@
   _ElementScanner(this.scanner);
   void scanLibrary(LibraryElement library) => scanner.scanLibrary(library);
   void scanUnit(CompilationUnitElement unit) => scanner.scan(unit);
 }
 
 class _EmptyEnvironment implements Environment {
   const _EmptyEnvironment();
 
   String valueOf(String key) => null;
 }