Always initialize the EventHandler in the standalone.

sdk/lib/_internal/lib/io_patch.dart

Index: sdk/lib/_internal/lib/io_patch.dart
diff --git a/sdk/lib/_internal/lib/io_patch.dart b/sdk/lib/_internal/lib/io_patch.dart
index e41a2ce63e58d11cfe4b6f7ddf0bf3f1b4bbe629..5f3e50d11f0865152b21c24fd8f10e103083f786 100644
--- a/sdk/lib/_internal/lib/io_patch.dart
+++ b/sdk/lib/_internal/lib/io_patch.dart
@@ -33,13 +33,9 @@ patch class _Directory {
 }
 
 patch class _EventHandler {
-  patch static void _start() {
-    throw new UnsupportedError("EventHandler._start");
-  }
-
-  patch static _sendData(Object sender,
-                         ReceivePort receivePort,
-                         int data) {
+  patch static void _sendData(Object sender,
+                              ReceivePort receivePort,
+                              int data) {
     throw new UnsupportedError("EventHandler._sendData");
   }
 }