Add gyp build for sample-extension.

dart.gyp

 # Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 {
   'targets': [
     {
       'target_name': 'compiler',
       'type': 'none',
       'dependencies': [
         'compiler/dart-compiler.gyp:dartc',
       ],
       'actions': []
     },
     {
       'target_name': 'runtime',
       'type': 'none',
       'dependencies': [
         'runtime/dart-runtime.gyp:dart',
         'runtime/dart-runtime.gyp:run_vm_tests',
         'runtime/dart-runtime.gyp:process_test',
+        'runtime/dart-runtime.gyp:test_extension',
+        'runtime/dart-runtime.gyp:sample_extension',
       ],
     },
     {
       # Build the SDK. This target is separate from upload_sdk as the
       # editor needs to build the SDK without uploading it.
       'target_name': 'create_sdk',
       'type': 'none',
       'dependencies': [
         'runtime/dart-runtime.gyp:dart',
         'dart2js',
@@ skipping 62 matching lines @@
     },
     {
       'target_name': 'api_docs',
       'type': 'none',
       'dependencies': [
         'utils/apidoc/apidoc.gyp:api_docs',
       ],
     }
   ],
 }