Change to <- for types.

pkg/compiler/lib/src/dart2js.dart

Index: pkg/compiler/lib/src/dart2js.dart
diff --git a/pkg/compiler/lib/src/dart2js.dart b/pkg/compiler/lib/src/dart2js.dart
index 9ee75e9b6f606c78119c5e75fff3ed671ddc7fb8..7cda7e9b4e3624ff46ed8a434f239b565831b693 100644
--- a/pkg/compiler/lib/src/dart2js.dart
+++ b/pkg/compiler/lib/src/dart2js.dart
@@ -40,7 +40,7 @@ String BUILD_ID = null;
  * string argument, or the arguments iterator for multiple arguments
  * handlers.
  */
-typedef void HandleOption(data);
+typedef HandleOption = void <- (dynamic data);
 
 class OptionHandler {
   final String pattern;
@@ -760,8 +760,8 @@ void main(List<String> arguments) {
   internalMain(arguments);
 }
 
-typedef void ExitFunc(int exitCode);
-typedef Future<api.CompilationResult> CompileFunc(
+typedef ExitFunc = void <- (int exitCode);
+typedef CompileFunc = Future<api.CompilationResult> <- (
     CompilerOptions compilerOptions,
     api.CompilerInput compilerInput,
     api.CompilerDiagnostics compilerDiagnostics,