Add pref entry for virtual keyboard

chrome/common/pref_names.cc

Index: chrome/common/pref_names.cc
diff --git a/chrome/common/pref_names.cc b/chrome/common/pref_names.cc
index d49a5f17176fb402d398a412d58ab9261b16ef82..27477d8f64f7ad8d321f4aeeae49d60ab1adfb12 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -474,6 +474,11 @@ const char kLanguageXkbAutoRepeatInterval[] =
 // "_r2" suffixes are added to the three prefs above when we change the
 // preferences not user-configurable, not to sync them with cloud.
 
+// A dictionary pref which determines a preferred virtual keyboard per layout.
+// e.g. { "xkb:us::eng": "http://asdfg..yuiop/" }
+const char kLanguagePreferredVirtualKeyboard[] =
+    "settings.language.preferred_virtual_keyboard";
+
 // A boolean pref which determines whether accessibility is enabled.
 const char kAccessibilityEnabled[] = "settings.accessibility";