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

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"
+
+namespace spellcheck {
+
+#if defined(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)
+
+}  // namespace spellcheck