Use `Function` as function type syntax.

pkg/compiler/lib/compiler.dart

Index: pkg/compiler/lib/compiler.dart
diff --git a/pkg/compiler/lib/compiler.dart b/pkg/compiler/lib/compiler.dart
index e0306730f4457d379fd51d524b8ff9b73ce953a1..d5306fdec015be026c6bec1a34b46e973986043f 100644
--- a/pkg/compiler/lib/compiler.dart
+++ b/pkg/compiler/lib/compiler.dart
@@ -29,10 +29,10 @@ import 'src/options.dart' show CompilerOptions;
  * expected to hold a zero element at the last position. If this is not the
  * case, the entire data structure is copied before scanning.
  */
-typedef Future/*<String | List<int>>*/ CompilerInputProvider(Uri uri);
+typedef CompilerInputProvider = Future/*<String | List<int>>*/ Function(Uri);
 
 /// Deprecated, please use [CompilerInputProvider] instead.
-typedef Future<String> ReadStringFromUri(Uri uri);
+typedef ReadStringFromUri = Future<String> Function(Uri);
 
 /**
  * Returns an [EventSink] that will serve as compiler output for the given
@@ -54,7 +54,7 @@ typedef Future<String> ReadStringFromUri(Uri uri);
  * As more features are added to the compiler, new names and
  * extensions may be introduced.
  */
-typedef EventSink<String> CompilerOutputProvider(String name, String extension);
+typedef CompilerOutputProvider = EventSink<String> Function(String name, String extension);
 
 /**
  * Invoked by the compiler to report diagnostics. If [uri] is
@@ -66,14 +66,14 @@ typedef EventSink<String> CompilerOutputProvider(String name, String extension);
  * diagnostic message, and [kind] indicates indicates what kind of
  * diagnostic it is.
  */
-typedef void DiagnosticHandler(
-    Uri uri, int begin, int end, String message, Diagnostic kind);
+typedef DiagnosticHandler =
+    void Function(Uri, int begin, int end, String message, Diagnostic kind);
 
 /**
  * Provides a package lookup mechanism in the case that no package root or
  * package resolution configuration file are explicitly specified.
  */
-typedef Future<Packages> PackagesDiscoveryProvider(Uri uri);
+typedef PackagesDiscoveryProvider = Future<Packages> Function(Uri);
 
 /// Information resulting from the compilation.
 class CompilationResult {