readability-static-accessed-through-instance

We access std::string::npos through member variables in a couple places.
Fix it.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: I587f89e1580661aa311dfe4e06591ab38806e241
diff --git a/.clang-tidy b/.clang-tidy
index 9958891..b4e75ee 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -285,6 +285,7 @@
 readability-redundant-smartptr-get,
 readability-redundant-string-cstr,
 readability-redundant-string-init,
+readability-static-accessed-through-instance,
 readability-identifier-naming'
 
 WarningsAsErrors: '*'