Update some comments about variations headers API use.

components/feedback/feedback_uploader_chrome.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/feedback/feedback_uploader_chrome.h"
 
 #include <string>
 
 #include "base/callback.h"
 #include "base/command_line.h"
@@ skipping 42 matching lines @@
           post_url, net::URLFetcher::POST,
           new FeedbackUploaderDelegate(
               data, base::Bind(&FeedbackUploaderChrome::UpdateUploadTimer,
                                AsWeakPtr()),
               base::Bind(&FeedbackUploaderChrome::RetryReport, AsWeakPtr())))
           .release();
   data_use_measurement::DataUseUserData::AttachToFetcher(
       fetcher, data_use_measurement::DataUseUserData::FEEDBACK_UPLOADER);
   // Tell feedback server about the variation state of this install.
   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(),
                                      context_->IsOffTheRecord(), false,
                                      is_signed_in, &headers);
   fetcher->SetExtraRequestHeaders(headers.ToString());
 
   fetcher->SetUploadData(kProtoBufMimeType, data);
   fetcher->SetRequestContext(
       content::BrowserContext::GetDefaultStoragePartition(context_)->
           GetURLRequestContext());
   fetcher->SetLoadFlags(net::LOAD_DO_NOT_SAVE_COOKIES |
                         net::LOAD_DO_NOT_SEND_COOKIES);
   fetcher->Start();
 }
 
 }  // namespace feedback