Append variation headers when fetching snippets.

components/ntp_snippets/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/ntp_snippets_fetcher.h"
 
 #include <stdlib.h>
 
 #include "base/command_line.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/json/json_writer.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/metrics/sparse_histogram.h"
 #include "base/path_service.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/time/default_tick_clock.h"
 #include "base/values.h"
 #include "components/data_use_measurement/core/data_use_user_data.h"
 #include "components/ntp_snippets/ntp_snippets_constants.h"
 #include "components/ntp_snippets/switches.h"
 #include "components/signin/core/browser/profile_oauth2_token_service.h"
 #include "components/signin/core/browser/signin_manager.h"
 #include "components/signin/core/browser/signin_manager_base.h"
+#include "components/variations/net/variations_http_headers.h"
 #include "components/variations/variations_associated_data.h"
 #include "google_apis/google_api_keys.h"
 #include "net/base/load_flags.h"
 #include "net/http/http_request_headers.h"
 #include "net/http/http_response_headers.h"
 #include "net/http/http_status_code.h"
 #include "net/url_request/url_fetcher.h"
 #include "third_party/icu/source/common/unicode/uloc.h"
 #include "third_party/icu/source/common/unicode/utypes.h"
 
@@ skipping 290 matching lines @@
   url_fetcher_->SetLoadFlags(net::LOAD_DO_NOT_SEND_COOKIES |
                              net::LOAD_DO_NOT_SAVE_COOKIES);
 
   data_use_measurement::DataUseUserData::AttachToFetcher(
       url_fetcher_.get(), data_use_measurement::DataUseUserData::NTP_SNIPPETS);
 
   HttpRequestHeaders headers;
   if (!auth_header.empty())
     headers.SetHeader("Authorization", auth_header);
   headers.SetHeader("Content-Type", "application/json; charset=UTF-8");
+  // Add X-Client-Data header with experiment IDs from field trials.
+  variations::AppendVariationHeaders(url,
+                                     false,  // incognito
+                                     false,  // uma_enabled
+                                     &headers);
   url_fetcher_->SetExtraRequestHeaders(headers.ToString());
   url_fetcher_->SetUploadData("application/json", request);
   // Log the request for debugging network issues.
   VLOG(1) << "Sending a NTP snippets request to " << url << ":" << std::endl
           << headers.ToString() << std::endl << request;
   // Fetchers are sometimes cancelled because a network change was detected.
   url_fetcher_->SetAutomaticallyRetryOnNetworkChanges(3);
   // Try to make fetching the files bit more robust even with poor connection.
   url_fetcher_->SetMaxRetriesOn5xx(3);
   url_fetcher_->Start();
@@ skipping 165 matching lines @@
                       tick_clock_->NowTicks() - fetch_start_time_);
   UMA_HISTOGRAM_ENUMERATION("NewTabPage.Snippets.FetchResult",
                             static_cast<int>(result),
                             static_cast<int>(FetchResult::RESULT_MAX));
 
   if (!snippets_available_callback_.is_null())
     snippets_available_callback_.Run(std::move(snippets));
 }
 
 }  // namespace ntp_snippets