Update some comments about variations headers API use.

components/omnibox/browser/search_provider.cc

 // Copyright 2012 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/omnibox/browser/search_provider.h"
 
 #include <stddef.h>
 #include <algorithm>
 #include <cmath>
 #include <utility>
@@ skipping 872 matching lines @@
   LogOmniboxSuggestRequest(REQUEST_SENT);
 
   std::unique_ptr<net::URLFetcher> fetcher =
       net::URLFetcher::Create(id, suggest_url, net::URLFetcher::GET, this);
   data_use_measurement::DataUseUserData::AttachToFetcher(
       fetcher.get(), data_use_measurement::DataUseUserData::OMNIBOX);
   fetcher->SetRequestContext(client()->GetRequestContext());
   fetcher->SetLoadFlags(net::LOAD_DO_NOT_SAVE_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(),
                                      client()->IsOffTheRecord(), false,
                                      is_signed_in, &headers);
   fetcher->SetExtraRequestHeaders(headers.ToString());
   fetcher->Start();
   return fetcher;
 }
 
 void SearchProvider::ConvertResultsToAutocompleteMatches() {
@@ skipping 595 matching lines @@
   for (MatchMap::const_iterator i(map.begin()); i != map.end(); ++i)
     matches.push_back(i->second);
   std::sort(matches.begin(), matches.end(), &AutocompleteMatch::MoreRelevant);
 
   // If there is a top scoring entry, find the corresponding answer.
   if (!matches.empty())
     return answers_cache_.GetTopAnswerEntry(matches[0].contents);
 
   return AnswersQueryData();
 }