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 c67b330356d2b080e673c5fde8b2a06bc22a8595..e18d4454314f4fdd8a7ce23fd7eac4eca4da825c 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -882,6 +882,9 @@ 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.