register voice interaction preference.

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 01dead67e7f6e015c2a0161e38144e435c030d12..5e057405bffa7a10022db66f13e750a588cccd76 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -63,6 +63,11 @@ const char kVoiceInteractionEnabled[] = "settings.voice_interaction.enabled";
 // voice interaction services.
 const char kVoiceInteractionContextEnabled[] =
     "settings.voice_interaction.context.enabled";
+// A preference indicating whether voice interaction settings have been read
+// from ARC. This synchronization only happens when user goes through the flow
+// to set up voice interaction.
+const char kVoiceInteractionPrefSynced[] =
+    "settings.voice_interaction.context.synced";
 #endif
 
 // A bool pref that keeps whether the child status for this profile was already