Update some comments about variations headers API use.

components/autofill/core/browser/autofill_download_manager.cc

Index: components/autofill/core/browser/autofill_download_manager.cc
diff --git a/components/autofill/core/browser/autofill_download_manager.cc b/components/autofill/core/browser/autofill_download_manager.cc
index 331de9984500330b84b5a68b287e47b68a6b502d..07084c52be49d39dcfe3cd57cda9e02a79775cbd 100644
--- a/components/autofill/core/browser/autofill_download_manager.cc
+++ b/components/autofill/core/browser/autofill_download_manager.cc
@@ -247,8 +247,8 @@ bool AutofillDownloadManager::StartRequest(
                         net::LOAD_DO_NOT_SEND_COOKIES);
   // Add Chrome experiment state to the request headers.
   net::HttpRequestHeaders headers;
-  // 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(fetcher->GetOriginalURL(),
                                      driver_->IsOffTheRecord(), false,