support multiple log message handlers in base/logging.h

base/logging.h

Index: base/logging.h
diff --git a/base/logging.h b/base/logging.h
index 714545c02bb06ac7f1b31e8a007b671e6dc11d6d..f8b9ec4c95d49bdba9b57e51c40ba1b92f8dfe10 100644
--- a/base/logging.h
+++ b/base/logging.h
@@ -284,9 +284,11 @@ BASE_EXPORT void SetLogAssertHandler(LogAssertHandlerFunction handler);
 // Returns true to signal that it handled the message and the message
 // should not be sent to other log destinations.
 typedef bool (*LogMessageHandlerFunction)(int severity,
-    const char* file, int line, size_t message_start, const std::string& str);
-BASE_EXPORT void SetLogMessageHandler(LogMessageHandlerFunction handler);
-BASE_EXPORT LogMessageHandlerFunction GetLogMessageHandler();
+                                          const std::string& file,
+                                          int line,
+                                          const std::string& str);
+BASE_EXPORT void AddLogMessageHandler(LogMessageHandlerFunction handler);
+BASE_EXPORT void RemoveLogMessageHandler(LogMessageHandlerFunction handler);
 
 typedef int LogSeverity;
 const LogSeverity LOG_VERBOSE = -1;  // This is level 1 verbosity