Fix variations seed being reset on a 304 response.

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"
@@ skipping 269 matching lines @@
       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) {
+  }
+
+  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);
 
@@ skipping 13 matching lines @@
   // to call this method again until another failed attempt occurs.
   DVLOG(1) << "Retrying fetch.";
   DoActualFetch();
   if (timer_.IsRunning())
     timer_.Reset();
 }
 
 bool VariationsService::StoreSeedData(const std::string& seed_data,
                                       const base::Time& seed_date,
                                       PrefService* local_prefs) {
+  if (seed_data.empty()) {
+    VLOG(1) << "Variations Seed data from server is empty, rejecting the seed.";
+    return false;
+  }
+
   // Only store the seed data if it parses correctly.
   TrialsSeed seed;
   if (!seed.ParseFromString(seed_data)) {
     VLOG(1) << "Variations Seed data from server is not in valid proto format, "
             << "rejecting the seed.";
     return false;
   }
 
   std::string base64_seed_data;
   if (!base::Base64Encode(seed_data, &base64_seed_data)) {
@@ skipping 245 matching lines @@
                                       variation_id);
     }
   }
 
   trial->SetForced();
   if (IsStudyExpired(study, reference_date))
     trial->Disable();
 }
 
 }  // namespace chrome_variations