Convert spellcheck to a buildflag header.

components/spellcheck/common/spellcheck_switches.cc

 // Copyright 2016 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.
 
 #include "build/build_config.h"
 #include "components/spellcheck/common/spellcheck_switches.h"
+#include "components/spellcheck/spellcheck_build_features.h"
 
 namespace spellcheck {
 namespace switches {
 
-#if defined(ENABLE_SPELLCHECK)
+#if BUILDFLAG(ENABLE_SPELLCHECK)
 // Enables participation in the field trial for user feedback to spelling
 // service.
 const char kEnableSpellingFeedbackFieldTrial[] =
     "enable-spelling-feedback-field-trial";
 
 // Specifies the number of seconds between sending batches of feedback to
 // spelling service. The default is 30 minutes. The minimum is 5 seconds. This
 // switch is for temporary testing only.
 // TODO(rouslan): Remove this flag when feedback testing is complete. Revisit by
 // August 2013.
 const char kSpellingServiceFeedbackIntervalSeconds[] =
     "spelling-service-feedback-interval-seconds";
 
 // Specifies the URL where spelling service feedback data will be sent instead
 // of the default URL. This switch is for temporary testing only.
 // TODO(rouslan): Remove this flag when feedback testing is complete. Revisit by
 // August 2013.
 const char kSpellingServiceFeedbackUrl[] = "spelling-service-feedback-url";
-#endif  // defined(ENABLE_SPELLCHECK)
+#endif  // BUILDFLAG(ENABLE_SPELLCHECK)
 
 }  // namespace switches
 }  // namespace spellcheck