[Media Router] Conditionally enable mDNS on Windows.

chrome/browser/media/router/media_router.gyp

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'includes': [
     'media_router.gypi',
   ],
   'targets': [
     {
@@ skipping 19 matching lines @@
           'dependencies': [
             # media_router_type_converters.h needs the generated file.
             'media_router_mojo_gen',
             'media_router_mojo',
             '<(DEPTH)/extensions/extensions.gyp:extensions_browser',
           ],
           'sources': [
             '<@(media_router_non_android_sources)',
           ]
         }],
+        [ 'OS=="win"', {
+          'sources': [
+            '<@(media_router_win_sources)',
+          ],
+        }],
       ]
     },
     {
       # Mojo compiler for the Media Router internal API.
       'target_name': 'media_router_mojo_gen',
       'type': 'none',
       'sources': [
         'media_router.mojom',
       ],
       'includes': [
@@ skipping 35 matching lines @@
             '<(DEPTH)/extensions/extensions.gyp:extensions_common',
           ],
           'sources': [
             '<@(media_router_non_android_test_support_sources)',
           ]
         }],
       ]
     },
   ],
 }