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

chrome/installer/util/installation_validation_helper.cc

Index: chrome/installer/util/installation_validation_helper.cc
diff --git a/chrome/installer/util/installation_validation_helper.cc b/chrome/installer/util/installation_validation_helper.cc
index e0252e975b26380a34985e42d0343b4d41c1c0eb..c968c8308de4fa6a4855f7ea715c89f97d3da445 100644
--- a/chrome/installer/util/installation_validation_helper.cc
+++ b/chrome/installer/util/installation_validation_helper.cc
@@ -34,7 +34,6 @@ class FailureLogHelper {
                                       const std::string& str);
 
   static const logging::LogSeverity kViolationSeverity_;
-  static logging::LogMessageHandlerFunction old_message_handler_;
   static int old_min_log_level_;
 };
 
@@ -44,29 +43,21 @@ const logging::LogSeverity
     FailureLogHelper::kViolationSeverity_ = logging::LOG_ERROR;
 
 // static
-logging::LogMessageHandlerFunction
-    FailureLogHelper::old_message_handler_ = NULL;
-
-// static
 int FailureLogHelper::old_min_log_level_ =
     FailureLogHelper::kViolationSeverity_;
 
 FailureLogHelper::FailureLogHelper() {
-  LOG_ASSERT(old_message_handler_ == NULL);
-
   // The validator logs at ERROR level.  Ensure that it generates messages so we
   // can transform them into test failures.
   old_min_log_level_ = logging::GetMinLogLevel();
   if (old_min_log_level_ > kViolationSeverity_)
     logging::SetMinLogLevel(kViolationSeverity_);
 
-  old_message_handler_ = logging::GetLogMessageHandler();
-  logging::SetLogMessageHandler(&AddFailureForLogMessage);
+  logging::PushLogMessageHandler(&AddFailureForLogMessage);
 }
 
 FailureLogHelper::~FailureLogHelper() {
-  logging::SetLogMessageHandler(old_message_handler_);
-  old_message_handler_ = NULL;
+  logging::PopLogMessageHandler();
 
   if (old_min_log_level_ > kViolationSeverity_)
     logging::SetMinLogLevel(old_min_log_level_);
@@ -92,9 +83,6 @@ bool FailureLogHelper::AddFailureForLogMessage(int severity,
     return true;
   }
 
-  if (old_message_handler_ != NULL)
-    return (old_message_handler_)(severity, file, line, message_start, str);
-
   return false;
 }