[Android] Add AndroidSpellChecker feature to allow for gradual rollout using finch.

components/spellcheck/renderer/spellcheck.cc

Index: components/spellcheck/renderer/spellcheck.cc
diff --git a/components/spellcheck/renderer/spellcheck.cc b/components/spellcheck/renderer/spellcheck.cc
index 1ecfaa203cb06dd8b247a3b30bdc7be0db9868c4..4757dc65233ad55ae2a00df49dcd3370efbec9f5 100644
--- a/components/spellcheck/renderer/spellcheck.cc
+++ b/components/spellcheck/renderer/spellcheck.cc
@@ -19,6 +19,7 @@
 #include "base/threading/thread_task_runner_handle.h"
 #include "build/build_config.h"
 #include "components/spellcheck/common/spellcheck_common.h"
+#include "components/spellcheck/common/spellcheck_features.h"
 #include "components/spellcheck/common/spellcheck_messages.h"
 #include "components/spellcheck/common/spellcheck_result.h"
 #include "components/spellcheck/common/spellcheck_switches.h"
@@ -537,10 +538,7 @@ void SpellCheck::CreateTextCheckingResults(
 
 bool SpellCheck::IsSpellcheckEnabled() {
 #if defined(OS_ANDROID)
-  if (!base::CommandLine::ForCurrentProcess()->HasSwitch(
-          spellcheck::switches::kEnableAndroidSpellChecker)) {
-    return false;
-  }
+  if (!spellcheck::IsAndroidSpellCheckFeatureEnabled()) return false;
 #endif
   return spellcheck_enabled_;
 }