[NTP Snippets] Add histogram with fetch time

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 "base/command_line.h"
 #include "base/files/file_path.h"
 #include "base/files/file_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/switches.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"
 
@@ skipping 66 matching lines @@
 
 }  // namespace
 
 NTPSnippetsFetcher::NTPSnippetsFetcher(
     scoped_refptr<URLRequestContextGetter> url_request_context_getter,
     const ParseJSONCallback& parse_json_callback,
     bool is_stable_channel)
     : url_request_context_getter_(url_request_context_getter),
       parse_json_callback_(parse_json_callback),
       is_stable_channel_(is_stable_channel),
+      tick_clock_(new base::DefaultTickClock()),
       weak_ptr_factory_(this) {}
 
 NTPSnippetsFetcher::~NTPSnippetsFetcher() {}
 
 void NTPSnippetsFetcher::SetCallback(
     const SnippetsAvailableCallback& callback) {
   snippets_available_callback_ = callback;
 }
 
 void NTPSnippetsFetcher::FetchSnippetsFromHosts(
     const std::set<std::string>& hosts, int count) {
   std::string host_restricts;
+  fetch_start_time_ = tick_clock_->NowTicks();
   if (!base::CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kDontRestrict)) {
     if (hosts.empty()) {
       FetchFinished(OptionalSnippets(), FetchResult::EMPTY_HOSTS,
                     /*extra_message=*/std::string());
       return;
     }
     for (const std::string& host : hosts)
       host_restricts += base::StringPrintf(kHostRestrictFormat, host.c_str());
   }
@@ skipping 78 matching lines @@
   FetchFinished(
       OptionalSnippets(), FetchResult::JSON_PARSE_ERROR,
       /*extra_message=*/base::StringPrintf(" (error %s)", error.c_str()));
 }
 
 void NTPSnippetsFetcher::FetchFinished(OptionalSnippets snippets,
                                        FetchResult result,
                                        const std::string& extra_message) {
   DCHECK(result == FetchResult::SUCCESS || !snippets);
   last_status_ = FetchResultToString(result) + extra_message;
+
+  UMA_HISTOGRAM_TIMES("NewTabPage.Snippets.FetchTime",
+                      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