Update from https://crrev.com/328418

tools/clang/plugins/FindBadConstructsAction.cpp

Index: tools/clang/plugins/FindBadConstructsAction.cpp
diff --git a/tools/clang/plugins/FindBadConstructsAction.cpp b/tools/clang/plugins/FindBadConstructsAction.cpp
index 6c39d724b1a7a476287ce4d48365f8732374dbdd..812508410ec3e6245df4c05538fe0ac93662bde6 100644
--- a/tools/clang/plugins/FindBadConstructsAction.cpp
+++ b/tools/clang/plugins/FindBadConstructsAction.cpp
@@ -57,6 +57,8 @@ bool FindBadConstructsAction::ParseArgs(const CompilerInstance& instance,
       options_.with_ast_visitor = true;
     } else if (args[i] == "check-templates") {
       options_.check_templates = true;
+    } else if (args[i] == "warn-only") {
+      options_.warn_only = true;
     } else {
       parsed = false;
       llvm::errs() << "Unknown clang plugin argument: " << args[i] << "\n";