Componentize spellcheck [4]: spellcheck/browser and android java-side.

components/spellcheck/browser/pref_names.h

+// 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.
+
+#ifndef COMPONENTS_SPELLCHECK_BROWSER_PREF_NAMES_H
+#define COMPONENTS_SPELLCHECK_BROWSER_PREF_NAMES_H
+
+namespace spellcheck {
+namespace prefs {
+
+extern const char kEnableContinuousSpellcheck[];
+extern const char kSpellCheckDictionaries[];
+extern const char kSpellCheckDictionary[];
+extern const char kSpellCheckUseSpellingService[];
+
+}  // namespace prefs
+}  // namespace spellcheck
+
+#endif  // COMPONENTS_SPELLCHECK_BROWSER_PREF_NAMES_H