support multiple log message handlers in base/logging.h

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 81d043ac3945d3582b0a99c22f4adb22d1bd8a21..23abedea9a73ee70801b4932373b01b9230d163c 100644
--- a/base/trace_event/trace_event_unittest.cc
+++ b/base/trace_event/trace_event_unittest.cc
@@ -2820,7 +2820,9 @@ TEST_F(TraceEventTestFixture, ThreadOnceBlocking) {
 }
 
 std::string* g_log_buffer = NULL;
-bool MockLogMessageHandler(int, const char*, int, size_t,
+bool MockLogMessageHandler(int,
+                           const std::string,
+                           int,
                            const std::string& str) {
   if (!g_log_buffer)
     g_log_buffer = new std::string();
@@ -2829,9 +2831,7 @@ bool MockLogMessageHandler(int, const char*, int, size_t,
 }
 
 TEST_F(TraceEventTestFixture, EchoToConsole) {
-  logging::LogMessageHandlerFunction old_log_message_handler =
-      logging::GetLogMessageHandler();
-  logging::SetLogMessageHandler(MockLogMessageHandler);
+  logging::AddLogMessageHandler(MockLogMessageHandler);
 
   TraceLog::GetInstance()->SetEnabled(
       TraceConfig(kRecordAllCategoryFilter, ECHO_TO_CONSOLE),
@@ -2854,20 +2854,20 @@ TEST_F(TraceEventTestFixture, EchoToConsole) {
 
   EndTraceAndFlush();
   delete g_log_buffer;
-  logging::SetLogMessageHandler(old_log_message_handler);
+  logging::RemoveLogMessageHandler(MockLogMessageHandler);
   g_log_buffer = NULL;
 }
 
-bool LogMessageHandlerWithTraceEvent(int, const char*, int, size_t,
+bool LogMessageHandlerWithTraceEvent(int,
+                                     const std::string&,
+                                     int,
                                      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::AddLogMessageHandler(LogMessageHandlerWithTraceEvent);
 
   TraceLog::GetInstance()->SetEnabled(
       TraceConfig(kRecordAllCategoryFilter, ECHO_TO_CONSOLE),
@@ -2878,7 +2878,7 @@ TEST_F(TraceEventTestFixture, EchoToConsoleTraceEventRecursion) {
   }
 
   EndTraceAndFlush();
-  logging::SetLogMessageHandler(old_log_message_handler);
+  logging::RemoveLogMessageHandler(LogMessageHandlerWithTraceEvent);
 }
 
 TEST_F(TraceEventTestFixture, TimeOffset) {