Componentize spellcheck [1]: create component and move switches there.

components/spellcheck.gypi

Index: components/spellcheck.gypi
diff --git a/components/spellcheck.gypi b/components/spellcheck.gypi
new file mode 100644
index 0000000000000000000000000000000000000000..064f3c7ee7262195d5fc2ea698b6c51fd7f3ab40
--- /dev/null
+++ b/components/spellcheck.gypi
@@ -0,0 +1,20 @@
+# 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.
+
+{
+  'targets': [
+    {
+      # GN version: //components/spellcheck/common
+      'target_name': 'spellcheck_common',
+      'type': 'static_library',
+      'include_dirs': [
+        '..',
+      ],
+      'sources': [
+        'spellcheck/common/spellcheck_switches.cc',
+        'spellcheck/common/spellcheck_switches.h',
+      ],
+    },
+  ],
+}