Dart: Moves |native| methods to patch files.

mojo/dart/embedder/core/buffer_patch.dart

Index: mojo/dart/embedder/core/buffer_patch.dart
diff --git a/mojo/dart/embedder/core/buffer_patch.dart b/mojo/dart/embedder/core/buffer_patch.dart
index fd34d1f948f5ec7f1a52aa9c11ace583055636de..4cb9dca9431cde641baee63456c7866723377074 100644
--- a/mojo/dart/embedder/core/buffer_patch.dart
+++ b/mojo/dart/embedder/core/buffer_patch.dart
@@ -2,3 +2,20 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+patch class _MojoSharedBufferNatives {
+  static List Create(int numBytes, int flags)
+      native "MojoSharedBuffer_Create";
+
+  static List Duplicate(int bufferHandle, int flags)
+      native "MojoSharedBuffer_Duplicate";
+
+  static List Map(MojoSharedBuffer buffer,
+                  int bufferHandle,
+                  int offset,
+                  int numBytes,
+                  int flags)
+      native "MojoSharedBuffer_Map";
+
+  static int Unmap(ByteData buffer)
+      native "MojoSharedBuffer_Unmap";
+}