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..11e8e3e4d3a0442699d96b67f9e128e5561141a5 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,
+void LogEventProvider::WinLogMessageListener::OnMessage(
+    logging::LogSeverity severity,
+    const char* file,
+    int line,
+    size_t message_start,
     const std::string& message) {
   EtwEventLevel level = TRACE_LEVEL_NONE;
 
@@ -51,7 +57,7 @@ bool LogEventProvider::LogMessage(logging::LogSeverity severity,
   // or if we're post-atexit handling.
   LogEventProvider* provider = LogEventProvider::GetInstance();
   if (provider == NULL || level > provider->enable_level())
-    return false;
+    return;
 
   // And now log the event.
   if (provider->enable_flags() & ENABLE_LOG_MESSAGE_ONLY) {
@@ -88,11 +94,7 @@ bool LogEventProvider::LogMessage(logging::LogSeverity severity,
     provider->Log(event.get());
   }
 
-  // Don't increase verbosity in other log destinations.
-  if (severity < provider->old_log_level_)
-    return true;
-
-  return false;
+  // The log verbosity for other log destinations is increased.
 }
 
 void LogEventProvider::Initialize(const GUID& provider_name) {
@@ -101,12 +103,14 @@ void LogEventProvider::Initialize(const GUID& provider_name) {
   provider->set_provider_name(provider_name);
   provider->Register();
 
-  // Register our message handler with logging.
-  SetLogMessageHandler(LogMessage);
+  // Register our message listener with logging.
+  provider->log_listener_ = base::MakeUnique<WinLogMessageListener>();
 }
 
 void LogEventProvider::Uninitialize() {
-  LogEventProvider::GetInstance()->Unregister();
+  LogEventProvider* provider = LogEventProvider::GetInstance();
+  provider->Unregister();
+  provider->log_listener_.reset();
 }
 
 void LogEventProvider::OnEventsEnabled() {