Give access to a network time kept in the variation service.

chrome/browser/metrics/variations/variations_service.cc

 // Copyright (c) 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 "chrome/browser/metrics/variations/variations_service.h"
 
 #include <set>
 
 #include "base/base64.h"
 #include "base/build_time.h"
 #include "base/command_line.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram.h"
 #include "base/version.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/metrics/proto/trials_seed.pb.h"
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/metrics/variations/variations_util.h"
 #include "chrome/common/pref_names.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/common/url_fetcher.h"
 #include "googleurl/src/gurl.h"
 #include "net/base/load_flags.h"
 #include "net/base/network_change_notifier.h"
 #include "net/http/http_response_headers.h"
+#include "net/http/http_status_code.h"
 #include "net/http/http_util.h"
 #include "net/url_request/url_fetcher.h"
 #include "net/url_request/url_request_status.h"
 
 namespace chrome_variations {
 
 namespace {
 
 // Default server of Variations seed info.
 const char kDefaultVariationsServerURL[] =
     "https://clients4.google.com/chrome-variations/seed";
 const int kMaxRetrySeedFetch = 5;
 
 // Time between seed fetches, in hours.
 const int kSeedFetchPeriodHours = 5;
 
+// TODO(mad): To be removed when we stop updating the NetworkTimeTracker.
+// For the HTTP date headers, the resolution of the server time is 1 second.
+const int64 kServerTimeResolutionMs = 1000;
+
 // Maps Study_Channel enum values to corresponding chrome::VersionInfo::Channel
 // enum values.
 chrome::VersionInfo::Channel ConvertStudyChannelToVersionChannel(
     Study_Channel study_channel) {
   switch (study_channel) {
     case Study_Channel_CANARY:
       return chrome::VersionInfo::CHANNEL_CANARY;
     case Study_Channel_DEV:
       return chrome::VersionInfo::CHANNEL_DEV;
     case Study_Channel_BETA:
@@ skipping 126 matching lines @@
   DCHECK(create_trials_from_seed_called_);
 
   // Perform the first fetch.
   FetchVariationsSeed();
 
   // Repeat this periodically.
   timer_.Start(FROM_HERE, base::TimeDelta::FromHours(kSeedFetchPeriodHours),
                this, &VariationsService::FetchVariationsSeed);
 }
 
+bool VariationsService::GetNetworkTime(base::Time* network_time,
+                                       base::TimeDelta* uncertainty) const {
+  return network_time_tracker_.GetNetworkTime(network_time, uncertainty);
+}
+
 #if defined(OS_WIN)
 void VariationsService::StartGoogleUpdateRegistrySync() {
   registry_syncer_.RequestRegistrySync();
 }
 #endif
 
 void VariationsService::SetCreateTrialsFromSeedCalledForTesting(bool called) {
   create_trials_from_seed_called_ = called;
 }
 
@@ skipping 49 matching lines @@
   DCHECK_EQ(pending_seed_request_.get(), source);
   // The fetcher will be deleted when the request is handled.
   scoped_ptr<const net::URLFetcher> request(
       pending_seed_request_.release());
   if (request->GetStatus().status() != net::URLRequestStatus::SUCCESS) {
     DVLOG(1) << "Variations server request failed.";
     return;
   }
 
   // Log the response code.
+  const int response_code = request->GetResponseCode();
   UMA_HISTOGRAM_CUSTOM_ENUMERATION("Variations.SeedFetchResponseCode",
-      net::HttpUtil::MapStatusCodeForHistogram(request->GetResponseCode()),
+      net::HttpUtil::MapStatusCodeForHistogram(response_code),
       net::HttpUtil::GetStatusCodesForHistogram());
 
   const base::TimeDelta latency =
       base::TimeTicks::Now() - last_request_started_time_;
 
-  if (request->GetResponseCode() != 200) {
-    DVLOG(1) << "Variations server request returned non-200 response code: "
-             << request->GetResponseCode();
-    if (request->GetResponseCode() == 304)
+  base::Time response_date;
+  if (response_code == net::HTTP_OK ||
+      response_code == net::HTTP_NOT_MODIFIED) {
+    bool success = request->GetResponseHeaders()->GetDateValue(&response_date);
+    DCHECK(success || response_date.is_null());
+
+    if (!response_date.is_null()) {
+      network_time_tracker_.UpdateNetworkTime(
+          response_date,
+          base::TimeDelta::FromMilliseconds(kServerTimeResolutionMs),
+          latency);
+    }
+  } else if (response_code != net::HTTP_OK) {
+    DVLOG(1) << "Variations server request returned non-HTTP_OK response code: "
+             << response_code;
+    if (response_code == net::HTTP_NOT_MODIFIED)
       UMA_HISTOGRAM_MEDIUM_TIMES("Variations.FetchNotModifiedLatency", latency);
     else
       UMA_HISTOGRAM_MEDIUM_TIMES("Variations.FetchOtherLatency", latency);
     return;
   }
   UMA_HISTOGRAM_MEDIUM_TIMES("Variations.FetchSuccessLatency", latency);
 
   std::string seed_data;
   bool success = request->GetResponseAsString(&seed_data);
   DCHECK(success);
 
-  base::Time response_date;
-  success = request->GetResponseHeaders()->GetDateValue(&response_date);
-  DCHECK(success || response_date.is_null());
-
   StoreSeedData(seed_data, response_date, g_browser_process->local_state());
 }
 
 void VariationsService::OnResourceRequestsAllowed() {
   // Note that this only attempts to fetch the seed at most once per period
   // (kSeedFetchPeriodHours). This works because
   // |resource_request_allowed_notifier_| only calls this method if an
   // attempt was made earlier that fails (which implies that the period had
   // elapsed). After a successful attempt is made, the notifier will know not
   // to call this method again until another failed attempt occurs.
@@ skipping 264 matching lines @@
                                       variation_id);
     }
   }
 
   trial->SetForced();
   if (IsStudyExpired(study, reference_date))
     trial->Disable();
 }
 
 }  // namespace chrome_variations