Enable dcheck_always_on on Win 10 FYI bot.

scripts/slave/recipe_modules/chromium_tests/chromium_fyi.py

 # Copyright 2014 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.
 
 from . import steps
 
 RESULTS_URL = 'https://chromeperf.appspot.com'
 
 SPEC = {
   'settings': {
@@ skipping 1940 matching lines @@
       ],
       'testing': {
         'platform': 'linux',
       },
     },
 
 
     'Chromium Win 10': {
       'chromium_config': 'chromium',
       'gclient_config': 'chromium',
+      'GYP_DEFINES': {
+        'dcheck_always_on': '1',
+      },
       'chromium_config_kwargs': {
         'BUILD_CONFIG': 'Release',
         'TARGET_BITS': 64,
       },
       'test_generators': [
         steps.generate_gtest,
         steps.generate_script,
         steps.generate_isolated_script,
       ],
       'testing': {
@@ skipping 96 matching lines @@
       'compile_targets': [
         'chrome',
       ],
       'enable_swarming': True,
       'testing': {
         'platform': 'win',
       },
     },
   },
 }