Even more instrumentation to diagnose an Android render crash.

base/metrics/field_trial.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 "base/metrics/field_trial.h"
 
 #include <algorithm>
 
 #include "base/build_time.h"
+#include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/rand_util.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 
 namespace base {
 
 namespace {
 
@@ skipping 88 matching lines @@
 void CheckTrialGroup(const std::string& trial_name,
                      const std::string& trial_group,
                      std::map<std::string, std::string>* seen_states) {
   if (ContainsKey(*seen_states, trial_name)) {
     CHECK_EQ((*seen_states)[trial_name], trial_group) << trial_name;
   } else {
     (*seen_states)[trial_name] = trial_group;
   }
 }
 
+// A second copy of FieldTrialList::seen_states_ that is meant to outlive the
+// FieldTrialList object to determine if the inconsistency happens because there
+// might be multiple FieldTrialList objects.
+// TODO(asvitkine): Remove when crbug.com/359406 is resolved.
+base::LazyInstance<std::map<std::string, std::string>>::Leaky g_seen_states =
+    LAZY_INSTANCE_INITIALIZER;
+
+// Tracks whether |g_seen_states| is used. Defaults to false, because unit tests
+// will create multiple FieldTrialList instances.
+bool g_use_global_check_states = false;
+
 }  // namespace
 
 // statics
 const int FieldTrial::kNotFinalized = -1;
 const int FieldTrial::kDefaultGroupNumber = 0;
 bool FieldTrial::enable_benchmarking_ = false;
 
 int FieldTrialList::kNoExpirationYear = 0;
 
 //------------------------------------------------------------------------------
@@ skipping 203 matching lines @@
   while (!registered_.empty()) {
     RegistrationMap::iterator it = registered_.begin();
     it->second->Release();
     registered_.erase(it->first);
   }
   DCHECK_EQ(this, global_);
   global_ = NULL;
 }
 
 // static
+void FieldTrialList::EnableGlobalStateChecks() {
+  CHECK(!g_use_global_check_states);
+  g_use_global_check_states = true;
+}
+
+// static
 FieldTrial* FieldTrialList::FactoryGetFieldTrial(
     const std::string& trial_name,
     FieldTrial::Probability total_probability,
     const std::string& default_group_name,
     const int year,
     const int month,
     const int day_of_month,
     FieldTrial::RandomizationType randomization_type,
     int* default_group_number) {
   return FactoryGetFieldTrialWithRandomizationSeed(
@@ skipping 133 matching lines @@
               trial.group_name.find(kPersistentStringSeparator));
     if (trial.activated)
       output->append(1, kActivationMarker);
     trial.trial_name.AppendToString(output);
     output->append(1, kPersistentStringSeparator);
     trial.group_name.AppendToString(output);
     output->append(1, kPersistentStringSeparator);
 
     CheckTrialGroup(trial.trial_name.as_string(), trial.group_name.as_string(),
                     &global_->seen_states_);
+    if (g_use_global_check_states) {
+      CheckTrialGroup(trial.trial_name.as_string(),
+                      trial.group_name.as_string(), &g_seen_states.Get());
+    }
   }
 }
 
 // static
 void FieldTrialList::GetActiveFieldTrialGroups(
     FieldTrial::ActiveGroups* active_groups) {
   DCHECK(active_groups->empty());
   if (!global_)
     return;
   AutoLock auto_lock(global_->lock_);
@@ skipping 108 matching lines @@
     field_trial->group_reported_ = true;
   }
 
   if (!field_trial->enable_field_trial_)
     return;
 
   {
     AutoLock auto_lock(global_->lock_);
     CheckTrialGroup(field_trial->trial_name(),
                     field_trial->group_name_internal(), &global_->seen_states_);
+    if (g_use_global_check_states) {

[Nico, 2016/04/15 19:00:31]

should this block have a comment too?

[Alexei Svitkine (slow), 2016/04/15 20:28:45]

Done.

+      CheckTrialGroup(field_trial->trial_name(),
+                      field_trial->group_name_internal(), &g_seen_states.Get());
+    }
   }
   global_->observer_list_->Notify(
       FROM_HERE, &FieldTrialList::Observer::OnFieldTrialGroupFinalized,
       field_trial->trial_name(), field_trial->group_name_internal());
 }
 
 // static
 size_t FieldTrialList::GetFieldTrialCount() {
   if (!global_)
     return 0;
@@ skipping 26 matching lines @@
     return;
   }
   AutoLock auto_lock(global_->lock_);
   CHECK(!global_->PreLockedFind(trial->trial_name())) << trial->trial_name();
   trial->AddRef();
   trial->SetTrialRegistered();
   global_->registered_[trial->trial_name()] = trial;
 }
 
 }  // namespace base