Dart: Moves |native| methods to patch files.

mojo/dart/embedder/core/handle_patch.dart

Index: mojo/dart/embedder/core/handle_patch.dart
diff --git a/mojo/dart/embedder/core/handle_patch.dart b/mojo/dart/embedder/core/handle_patch.dart
index fd34d1f948f5ec7f1a52aa9c11ace583055636de..d496e4b8f3d4375df2d15de2ccd6fe629532c7e8 100644
--- a/mojo/dart/embedder/core/handle_patch.dart
+++ b/mojo/dart/embedder/core/handle_patch.dart
@@ -2,3 +2,12 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+patch class _MojoHandleNatives {
+  static int register(MojoEventStream eventStream) native "MojoHandle_Register";
+  static int close(int handle) native "MojoHandle_Close";
+  static List wait(int handle, int signals, int deadline)
+      native "MojoHandle_Wait";
+  static List waitMany(
+      List<int> handles, List<int> signals, int deadline)
+      native "MojoHandle_WaitMany";
+}