Allow multiple logging::LogMessage{Handler,Listener}s

base/trace_event/trace_event_unittest.cc

Index: base/trace_event/trace_event_unittest.cc
diff --git a/base/trace_event/trace_event_unittest.cc b/base/trace_event/trace_event_unittest.cc
index ff8ec2de78880d93f521dce452c719965af25151..40c99591d7eba4d7253c75f53c71cb1a7ffe6146 100644
--- a/base/trace_event/trace_event_unittest.cc
+++ b/base/trace_event/trace_event_unittest.cc
@@ -3037,18 +3037,15 @@ TEST_F(TraceEventTestFixture, ThreadOnceBlocking) {
 }
 
 std::string* g_log_buffer = NULL;
-bool MockLogMessageHandler(int, const char*, int, size_t,
-                           const std::string& str) {
+void MockLogMessageListener(int, const char*, int, size_t,
+                            const std::string& str) {
   if (!g_log_buffer)
     g_log_buffer = new std::string();
   g_log_buffer->append(str);
-  return false;
 }
 
 TEST_F(TraceEventTestFixture, EchoToConsole) {
-  logging::LogMessageHandlerFunction old_log_message_handler =
-      logging::GetLogMessageHandler();
-  logging::SetLogMessageHandler(MockLogMessageHandler);
+  logging::ScopedLogMessageListener l(MockLogMessageListener);
 
   TraceLog::GetInstance()->SetEnabled(
       TraceConfig(kRecordAllCategoryFilter, ECHO_TO_CONSOLE),
@@ -3071,20 +3068,16 @@ TEST_F(TraceEventTestFixture, EchoToConsole) {
 
   EndTraceAndFlush();
   delete g_log_buffer;
-  logging::SetLogMessageHandler(old_log_message_handler);
   g_log_buffer = NULL;
 }
 
-bool LogMessageHandlerWithTraceEvent(int, const char*, int, size_t,
+void LogMessageListenerWithTraceEvent(int, const char*, int, size_t,
                                      const std::string&) {
   TRACE_EVENT0("log", "trace_event");
-  return false;
 }
 
 TEST_F(TraceEventTestFixture, EchoToConsoleTraceEventRecursion) {
-  logging::LogMessageHandlerFunction old_log_message_handler =
-      logging::GetLogMessageHandler();
-  logging::SetLogMessageHandler(LogMessageHandlerWithTraceEvent);
+  logging::ScopedLogMessageListener l(LogMessageListenerWithTraceEvent);
 
   TraceLog::GetInstance()->SetEnabled(
       TraceConfig(kRecordAllCategoryFilter, ECHO_TO_CONSOLE),
@@ -3095,7 +3088,6 @@ TEST_F(TraceEventTestFixture, EchoToConsoleTraceEventRecursion) {
   }
 
   EndTraceAndFlush();
-  logging::SetLogMessageHandler(old_log_message_handler);
 }
 
 TEST_F(TraceEventTestFixture, TimeOffset) {