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

remoting/host/native_messaging/log_message_handler.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "remoting/host/native_messaging/log_message_handler.h"
 
 #include "base/bind.h"
 #include "base/lazy_instance.h"
 #include "base/strings/string_util.h"
 #include "base/synchronization/lock.h"
@@ skipping 18 matching lines @@
     const Delegate& delegate)
     : delegate_(delegate),
       suppress_logging_(false),
       caller_task_runner_(base::ThreadTaskRunnerHandle::Get()),
       weak_ptr_factory_(this) {
   base::AutoLock lock(g_log_message_handler_lock.Get());
   if (g_log_message_handler) {
     LOG(FATAL) << "LogMessageHandler is already registered. Only one instance "
                << "per process is allowed.";
   }
-  previous_log_message_handler_ = logging::GetLogMessageHandler();
-  logging::SetLogMessageHandler(&LogMessageHandler::OnLogMessage);
+  logging::PushLogMessageHandler(&LogMessageHandler::OnLogMessage);
   g_log_message_handler = this;
 }
 
 LogMessageHandler::~LogMessageHandler() {
   base::AutoLock lock(g_log_message_handler_lock.Get());
-  if (logging::GetLogMessageHandler() != &LogMessageHandler::OnLogMessage) {
+  if (logging::GetTopLogMessageHandler() != &LogMessageHandler::OnLogMessage) {
     LOG(FATAL) << "LogMessageHandler is not the top-most message handler. "
                << "Cannot unregister.";
   }

[Dan Beam, 2016/07/15 03:11:19]

^ do we still need this?

[wychen, 2016/07/18 15:44:12]

Cleaned this up to simplify logic.

-  logging::SetLogMessageHandler(previous_log_message_handler_);
+  logging::PopLogMessageHandler(&LogMessageHandler::OnLogMessage);
   g_log_message_handler = nullptr;
 }
 
 // static
 const char* LogMessageHandler::kDebugMessageTypeName = "_debug_log";
 
 // static
 bool LogMessageHandler::OnLogMessage(
     logging::LogSeverity severity,
     const char* file,
@@ skipping 62 matching lines @@
   dictionary->SetString("message", message);
   dictionary->SetString("file", file);
   dictionary->SetInteger("line", line);
 
   delegate_.Run(std::move(dictionary));
 
   suppress_logging_ = false;
 }
 
 }  // namespace remoting