[tracing] Fix races in TraceLog's EnabledStateObserver

base/trace_event/trace_log.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 "base/trace_event/trace_log.h"
 
 #include <algorithm>
 #include <cmath>
 
 #include "base/base_switches.h"
@@ skipping 790 matching lines @@
 }
 
 int TraceLog::GetNumTracesRecorded() {
   AutoLock lock(lock_);
   if (!IsEnabled())
     return -1;
   return num_traces_recorded_;
 }
 
 void TraceLog::AddEnabledStateObserver(EnabledStateObserver* listener) {
+  AutoLock lock(lock_);
   enabled_state_observer_list_.push_back(listener);
 }
 
 void TraceLog::RemoveEnabledStateObserver(EnabledStateObserver* listener) {
+  AutoLock lock(lock_);
   std::vector<EnabledStateObserver*>::iterator it =
       std::find(enabled_state_observer_list_.begin(),
                 enabled_state_observer_list_.end(), listener);
   if (it != enabled_state_observer_list_.end())
     enabled_state_observer_list_.erase(it);
 }
 
 bool TraceLog::HasEnabledStateObserver(EnabledStateObserver* listener) const {
+  AutoLock lock(lock_);
   std::vector<EnabledStateObserver*>::const_iterator it =
       std::find(enabled_state_observer_list_.begin(),
                 enabled_state_observer_list_.end(), listener);
   return it != enabled_state_observer_list_.end();
 }
 
 TraceLogStatus TraceLog::GetStatus() const {
   AutoLock lock(lock_);
   TraceLogStatus result;
   result.event_capacity = logged_events_->Capacity();
@@ skipping 936 matching lines @@
 }
 
 ScopedTraceBinaryEfficient::~ScopedTraceBinaryEfficient() {
   if (*category_group_enabled_) {
     TRACE_EVENT_API_UPDATE_TRACE_EVENT_DURATION(category_group_enabled_, name_,
                                                 event_handle_);
   }
 }
 
 }  // namespace trace_event_internal