Restrict transmission of external exp ids to signed in users.

components/ntp_snippets/remote/ntp_snippets_fetcher.cc

 // Copyright 2016 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/ntp_snippets/remote/ntp_snippets_fetcher.h"
 
 #include <cstdlib>
 #include <utility>
 
 #include "base/command_line.h"
@@ skipping 663 matching lines @@
 std::string NTPSnippetsFetcher::RequestBuilder::BuildHeaders() const {
   net::HttpRequestHeaders headers;
   headers.SetHeader("Content-Type", "application/json; charset=UTF-8");
   if (!auth_header_.empty()) {
     headers.SetHeader("Authorization", auth_header_);
   }
   // Add X-Client-Data header with experiment IDs from field trials.
   variations::AppendVariationHeaders(url_,
                                      false,  // incognito
                                      false,  // uma_enabled
+                                     false,  // is_signed_in

[Marc Treib, 2016/12/09 12:34:31]

Essentially the same comment that mathp had: Can you please add a comment
explaining why it's okay to simply set this to false here? I was also concerned
that this would stop variations from working.

[Alexei Svitkine (slow), 2016/12/09 15:53:58]

Done.

                                      &headers);
   return headers.ToString();
 }
 
 std::string NTPSnippetsFetcher::RequestBuilder::BuildBody() const {
   auto request = base::MakeUnique<base::DictionaryValue>();
   std::string user_locale = PosixLocaleFromBCP47Language(params_.language_code);
   switch (fetch_api_) {
     case NTPSnippetsFetcher::CHROME_READER_API: {
       auto content_params = base::MakeUnique<base::DictionaryValue>();
@@ skipping 403 matching lines @@
   NOTREACHED();
   return false;
 }
 
 bool NTPSnippetsFetcher::NeedsAuthentication() const {
   return (personalization_ == Personalization::kPersonal ||
           personalization_ == Personalization::kBoth);
 }
 
 }  // namespace ntp_snippets