Add a very basic PIN UI implementation that is shared between lock and settings.

chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc

Index: chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
diff --git a/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc b/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
index 9c94d2372402c665235d70e22f398c04b26d20df..abb3532860f97bdd6b98f9163fc66e2201217d7a 100644
--- a/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
+++ b/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
@@ -468,6 +468,8 @@ void SigninScreenHandler::DeclareLocalizedValues(
 
 void SigninScreenHandler::RegisterMessages() {
   AddCallback("authenticateUser", &SigninScreenHandler::HandleAuthenticateUser);
+  AddCallback("authenticateUserWithPin",
+              &SigninScreenHandler::HandleAuthenticateUserWithPin);
   AddCallback("launchIncognito", &SigninScreenHandler::HandleLaunchIncognito);
   AddCallback("showSupervisedUserCreationScreen",
               &SigninScreenHandler::HandleShowSupervisedUserCreationScreen);
@@ -1008,6 +1010,17 @@ void SigninScreenHandler::HandleAuthenticateUser(const AccountId& account_id,
   delegate_->Login(user_context, SigninSpecifics());
 }
 
+void SigninScreenHandler::HandleAuthenticateUserWithPin(
+    const AccountId& account_id, const std::string& password) {
+  if (!delegate_)
+    return;
+  DCHECK_EQ(account_id.GetUserEmail(),
+            gaia::SanitizeEmail(account_id.GetUserEmail()));
+
+  // TODO(jdufault): Implement this.
+  NOTIMPLEMENTED();
+}
+
 void SigninScreenHandler::HandleLaunchIncognito() {
   UserContext context(user_manager::USER_TYPE_GUEST, EmptyAccountId());
   if (delegate_)