Build uses dart2js.bat on Windows

utils/apidoc/apidoc.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.
 
 {
+  'variables' : {
+    'script_suffix%': '',
+  },
+  'conditions' : [
+    ['OS=="win"', {
+      'variables' : {
+        'script_suffix': '.bat',
+      },
+    }],
+  ],
   'targets': [
     {
       'target_name': 'api_docs',
       'type': 'none',
       'dependencies': [
         '../../utils/compiler/compiler.gyp:dart2js',
         '../../runtime/dart-runtime.gyp:dart',
       ],
       'includes': [
         '../../corelib/src/corelib_sources.gypi',
       ],
       'actions': [
         {
           'action_name': 'run_apidoc',
           'inputs': [
             '<(PRODUCT_DIR)/<(EXECUTABLE_PREFIX)dart<(EXECUTABLE_SUFFIX)',
             '<(PRODUCT_DIR)/dart2js',
+            '<(PRODUCT_DIR)/dart2js.bat',
             '<!@(["python", "../../tools/list_files.py", "\\.(css|ico|js|json|png|sh|txt|yaml|py)$", ".", "../../lib/dartdoc"])',
             '<!@(["python", "../../tools/list_files.py", "\\.dart$", "../../lib", "../../runtime/lib", "../../runtime/bin"])',
-            '<@(_sources)',
           ],
           'outputs': [
             '<(PRODUCT_DIR)/api_docs/index.html',
             '<(PRODUCT_DIR)/api_docs/client-live-nav.js',
           ],
           'action': [
             '<(PRODUCT_DIR)/<(EXECUTABLE_PREFIX)dart<(EXECUTABLE_SUFFIX)',
             'apidoc.dart',
             '--out=<(PRODUCT_DIR)/api_docs',
             '--mode=live-nav',
-            '--compiler=<(PRODUCT_DIR)/dart2js',
+            '--compiler=<(PRODUCT_DIR)/dart2js<(script_suffix)',
           ],
+          'message': 'Running apidoc: <(_action)',
         },
       ],
     }
   ],
 }