Add is_chromecast to GN build.

chrome/chrome_tests.gypi

 # Copyright 2013 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.
 {
   'variables': {
     'chrome_browser_extensions_test_support_sources': [
       # A list of sources which is shared between different browser tests.
       'browser/apps/app_browsertest_util.cc',
       'browser/apps/app_browsertest_util.h',
       'browser/extensions/browsertest_util.cc',
@@ skipping 2504 matching lines @@
             'test/data/webui/print_preview.h',
             'test/data/webui/print_preview.js',
           ],
         }],
         ['enable_media_router==1', {
           'sources': [ '<@(chrome_browser_tests_media_router_sources)' ],
           'dependencies': [
             'browser/media/router/media_router.gyp:media_router_test_support',
             'test/media_router/media_router_tests.gypi:media_router_integration_test_files'
           ],
-          'conditions': [
-            ['toolkit_views==0', {
-              'sources!': [ 'browser/ui/views/media_router/media_router_ui_browsertest.cc' ],
-            }],
-          ],
         }],
         ['enable_mdns==1', {
           'sources' : [
             'browser/ui/webui/local_discovery/local_discovery_ui_browsertest.cc',
           ]
         }],
         [ 'use_brlapi==0', {
           'sources!': [
             'browser/extensions/api/braille_display_private/braille_display_private_apitest.cc'
             ]
@@ skipping 819 matching lines @@
             'utility',
           ],
           'sources': [
             'tools/service_discovery_sniffer/service_discovery_sniffer.cc',
             'tools/service_discovery_sniffer/service_discovery_sniffer.h',
           ],
         }]
     }],
   ],  # 'conditions'
 }