Update some comments about variations headers API use.

components/ntp_snippets/remote/ntp_snippets_json_request.cc

Index: components/ntp_snippets/remote/ntp_snippets_json_request.cc
diff --git a/components/ntp_snippets/remote/ntp_snippets_json_request.cc b/components/ntp_snippets/remote/ntp_snippets_json_request.cc
index 4d50f652efadf52d21daadaa22541a4d47ae1be2..7ac4f5cd3436ad42394faf919ae1620355d49744 100644
--- a/components/ntp_snippets/remote/ntp_snippets_json_request.cc
+++ b/components/ntp_snippets/remote/ntp_snippets_json_request.cc
@@ -356,8 +356,8 @@ std::string NTPSnippetsJsonRequest::Builder::BuildHeaders() const {
     headers.SetHeader("Authorization", auth_header_);
   }
   // Add X-Client-Data header with experiment IDs from field trials.
-  // Note: It's fine to pass in |is_signed_in| false, which does not affect
-  // transmission of experiment ids coming from the variations server.
+  // Note: It's OK to pass |is_signed_in| false if it's unknown, as it does
+  // not affect transmission of experiments coming from the variations server.
   bool is_signed_in = false;
   variations::AppendVariationHeaders(url_,
                                      false,  // incognito