Convert spellcheck to a buildflag header.

components/spellcheck/common/spellcheck_features.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 "components/spellcheck/common/spellcheck_features.h"
 
 #include "base/sys_info.h"
+#include "components/spellcheck/spellcheck_build_features.h"
 
 namespace spellcheck {
 
-#if defined(ENABLE_SPELLCHECK) && defined(OS_ANDROID)
+#if BUILDFLAG(ENABLE_SPELLCHECK) && defined(OS_ANDROID)
 
 // Enables/disables Android spellchecker.
 const base::Feature kAndroidSpellChecker{
     "AndroidSpellChecker", base::FEATURE_DISABLED_BY_DEFAULT};
 
 // Enables/disables Android spellchecker on non low-end Android devices.
 const base::Feature kAndroidSpellCheckerNonLowEnd{
     "AndroidSpellCheckerNonLowEnd", base::FEATURE_DISABLED_BY_DEFAULT};
 
 bool IsAndroidSpellCheckFeatureEnabled() {
   if (base::FeatureList::IsEnabled(
           spellcheck::kAndroidSpellCheckerNonLowEnd)) {
     return !base::SysInfo::IsLowEndDevice();
   }
 
   if (base::FeatureList::IsEnabled(
           spellcheck::kAndroidSpellChecker)) {
     return true;
   }
 
   return false;
 }
 
-#endif  // defined(ENABLE_SPELLCHECK) && defined(OS_ANDROID)
+#endif  // BUILDFLAG(ENABLE_SPELLCHECK) && defined(OS_ANDROID)
 
 }  // namespace spellcheck