Add persisted preference for projection touch HUD

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 c96e761baee48966f3143b9dcfba23b16ba20a9c..8c783a3e9c4ed17e5260193643d6674b74cb38e0 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -886,6 +886,9 @@ const char kAttestationEnabled[] = "attestation.enabled";
 // The list of extensions allowed to use the platformKeysPrivate API for
 // remote attestation.
 const char kAttestationExtensionWhitelist[] = "attestation.extension_whitelist";
+
+// A boolean pref indicating whether the projection touch HUD is enabled or not.
+const char kTouchHudProjectionEnabled[] = "touch_hud.projection_enabled";
 #endif  // defined(OS_CHROMEOS)
 
 // The disabled messages in IPC logging.