Add power-user keyboard mode for ChromeOS with Search key acting as a typical Fn key.

chrome/browser/chromeos/preferences.h

Index: chrome/browser/chromeos/preferences.h
diff --git a/chrome/browser/chromeos/preferences.h b/chrome/browser/chromeos/preferences.h
index dcee14c19e2d125927c80534a3d7f5739063372d..5ca89c30a1712018337f534a412a108ca4b7740a 100644
--- a/chrome/browser/chromeos/preferences.h
+++ b/chrome/browser/chromeos/preferences.h
@@ -141,6 +141,7 @@ class Preferences {
       language_prefs::kNumMozcMultipleChoicePrefs];
   IntegerPrefMember mozc_integer_prefs_[
       language_prefs::kNumMozcIntegerPrefs];
+  BooleanPrefMember search_key_acts_as_function_key_;
   BooleanPrefMember xkb_auto_repeat_enabled_;
   IntegerPrefMember xkb_auto_repeat_delay_pref_;
   IntegerPrefMember xkb_auto_repeat_interval_pref_;