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

base/logging_win.cc

Index: base/logging_win.cc
diff --git a/base/logging_win.cc b/base/logging_win.cc
index 319ae8a9d38186aa7ffc6466f574c2a795a1832c..d61e81880fd8aee317494e13fdc10a38714d23ab 100644
--- a/base/logging_win.cc
+++ b/base/logging_win.cc
@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 #include "base/logging_win.h"
+#include "base/memory/ptr_util.h"
 #include "base/memory/singleton.h"
 #include <initguid.h>  // NOLINT
 
@@ -17,13 +18,18 @@ DEFINE_GUID(kLogEventId,
 LogEventProvider::LogEventProvider() : old_log_level_(LOG_NONE) {
 }
 
+LogEventProvider::~LogEventProvider() {}
+
 LogEventProvider* LogEventProvider::GetInstance() {
   return base::Singleton<LogEventProvider, base::StaticMemorySingletonTraits<
                                                LogEventProvider>>::get();
 }
 
-bool LogEventProvider::LogMessage(logging::LogSeverity severity,
-    const char* file, int line, size_t message_start,
+bool LogEventProvider::WinLogMessageHandler::OnMessage(
+    logging::LogSeverity severity,
+    const char* file,
+    int line,
+    size_t message_start,
     const std::string& message) {
   EtwEventLevel level = TRACE_LEVEL_NONE;
 
@@ -88,7 +94,8 @@ bool LogEventProvider::LogMessage(logging::LogSeverity severity,
     provider->Log(event.get());
   }
 
-  // Don't increase verbosity in other log destinations.
+  // Don't increase verbosity in other log destinations below this handler
+  // in the handler stack.
   if (severity < provider->old_log_level_)
     return true;
 
@@ -102,11 +109,13 @@ void LogEventProvider::Initialize(const GUID& provider_name) {
   provider->Register();
 
   // Register our message handler with logging.
-  SetLogMessageHandler(LogMessage);
+  provider->log_handler_ = base::MakeUnique<WinLogMessageHandler>();
 }
 
 void LogEventProvider::Uninitialize() {
-  LogEventProvider::GetInstance()->Unregister();
+  LogEventProvider* provider = LogEventProvider::GetInstance();
+  provider->Unregister();
+  provider->log_handler_.reset();
 }
 
 void LogEventProvider::OnEventsEnabled() {