Add OnBeforeTraceLogDisabled notification to EnabledStateObserver

base/trace_event/trace_log.cc

Index: base/trace_event/trace_log.cc
diff --git a/base/trace_event/trace_log.cc b/base/trace_event/trace_log.cc
index 1a9af140551254bf6111c54ed4fb2a55d2e50121..8b8ef76c6f8b502618fb184f78898dc7602dc2df 100644
--- a/base/trace_event/trace_log.cc
+++ b/base/trace_event/trace_log.cc
@@ -818,7 +818,8 @@ TraceConfig TraceLog::GetCurrentTraceConfig() const {
 }
 
 void TraceLog::SetDisabled() {
-  AutoLock lock(lock_);
+  AutoLock lock1(disabling_lock_);
+  AutoLock lock2(lock_);
   SetDisabledWhileLocked();
 }
 
@@ -834,6 +835,18 @@ void TraceLog::SetDisabledWhileLocked() {
     return;
   }
 
+  std::vector<EnabledStateObserver*> observer_list =
+      enabled_state_observer_list_;
+  dispatching_to_observer_list_ = true;
+  {
+    // Dispatch to observers outside the lock in case the observer triggers a
+    // trace event.
+    AutoUnlock unlock(lock_);
+    for (EnabledStateObserver* observer : observer_list)
+      observer->OnBeforeTraceLogDisabled();
+  }
+  dispatching_to_observer_list_ = false;
+
   mode_ = DISABLED;
 
   if (sampling_thread_) {
@@ -855,12 +868,9 @@ void TraceLog::SetDisabledWhileLocked() {
   // Remove metadata events so they will not get added to a subsequent trace.
   metadata_events_.clear();
 
-  dispatching_to_observer_list_ = true;
-  std::vector<EnabledStateObserver*> observer_list =
-      enabled_state_observer_list_;
   std::map<AsyncEnabledStateObserver*, RegisteredAsyncObserver> observer_map =
       async_observers_;
-
+  dispatching_to_observer_list_ = true;
   {
     // Dispatch to observers outside the lock in case the observer triggers a
     // trace event.