Restrict transmission of external exp ids to signed in users.

chrome/browser/android/metrics/uma_session_stats.cc

 // Copyright 2015 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/android/metrics/uma_session_stats.h"
 
 #include "base/android/jni_array.h"
 #include "base/android/jni_string.h"
 #include "base/command_line.h"
 #include "base/metrics/histogram_macros.h"
@@ skipping 150 matching lines @@
   UMA_HISTOGRAM_COUNTS_100("UMA.ExternalExperiment.GroupCount",
                            experiment_ids.size());
 
   std::vector<uint32_t> group_name_hashes;
   group_name_hashes.reserve(experiment_ids.size());
 
   variations::ActiveGroupId active_group;
   active_group.name = metrics::HashName(trial_name_utf8);
   for (int experiment_id : experiment_ids) {
     active_group.group = metrics::HashName(base::IntToString(experiment_id));
+    // Since external experiments are not based on Chrome's low entropy source,
+    // they are only sent to Google web properties for signed in users to make
+    // sure that this couldn't be used to identify a user that's not signed in.
     variations::AssociateGoogleVariationIDForceHashes(
-        variations::GOOGLE_WEB_PROPERTIES, active_group,
+        variations::GOOGLE_WEB_PROPERTIES_SIGNED_IN, active_group,
         static_cast<variations::VariationID>(experiment_id));
     group_name_hashes.push_back(active_group.group);
   }
 
   UmaSessionStats::RegisterSyntheticMultiGroupFieldTrial(trial_name_utf8,
                                                          group_name_hashes);
 }
 
 static void RegisterSyntheticFieldTrial(
     JNIEnv* env,
@@ skipping 46 matching lines @@
   // We should have only one UmaSessionStats instance.
   DCHECK(!g_uma_session_stats);
   g_uma_session_stats = new UmaSessionStats();
   return reinterpret_cast<intptr_t>(g_uma_session_stats);
 }
 
 // Register native methods
 bool RegisterUmaSessionStats(JNIEnv* env) {
   return RegisterNativesImpl(env);
 }