Make the name of the event source for SYSLOG configurable.

base/syslog_logging.cc

Index: base/syslog_logging.cc
diff --git a/base/syslog_logging.cc b/base/syslog_logging.cc
index 1cd545910a967a6f52f5a138136bceb8be6782fd..17b750ded14bcd5de0894aac9d83d8b579f4c416 100644
--- a/base/syslog_logging.cc
+++ b/base/syslog_logging.cc
@@ -6,6 +6,8 @@
 #include "base/syslog_logging.h"
 
 #if defined(OS_WIN)
+#include "base/bind.h"
+#include "base/callback_helpers.h"
 #include "base/win/eventlog_messages.h"
 
 #include <windows.h>
@@ -19,6 +21,18 @@
 
 namespace logging {
 
+#if defined(OS_WIN)
+
+namespace {
+std::string* g_event_source_name = nullptr;
+}
+
+void SetEventSourceName(const std::string& name) {
+  DCHECK_EQ(nullptr, g_event_source_name);
+  g_event_source_name = new std::string(name);
+}
+#endif  // defined(OS_WIN)
+
 EventLogMessage::EventLogMessage(const char* file,
                                  int line,
                                  LogSeverity severity)
@@ -27,13 +41,23 @@ EventLogMessage::EventLogMessage(const char* file,
 
 EventLogMessage::~EventLogMessage() {
 #if defined(OS_WIN)
-  const char kEventSource[] = "chrome";
-  HANDLE event_log_handle = RegisterEventSourceA(NULL, kEventSource);
+  // If g_event_source_name is nullptr (which it is per default) SYSLOG will
+  // degrade gracefully to regular LOG with an extra error suffix. If you see

[Nico, 2016/12/02 03:08:41]

Is this useful? Why wouldn't this CHECK(false) instead?

The CL description currently says

"""
The default behavior of SYSLOG now is equivalent to LOG unless
SetEventSourceName is called at which point the function can start
logging to the Event Log as well.
"""

If every output is prefixed with " !!EVENTLOG SOURCE NAME NOT SET!!" that
doesn't seem equivalent to LOG. If this is a problem we should CHECK(false). If
it isn't, we shouldn't include the noise.

[pastarmovj, 2016/12/02 19:30:59]

I see this as a debugging facility for the debigging facility. :)
At best I see a NOTREACHED here but nothing that will run in release builds
because it be a shame to crash even once instance of chrome over this.

[Nico, 2016/12/02 20:28:58]

History shows that nobody looks at log spam. Either it's a bug when this is not
set, then this should be a (D)CHECK, or it's ok, then it shouldn't spam. See
also the section on CHECKs in
https://chromium.googlesource.com/chromium/src/+/master/styleguide/c++/c++.md
(which says "if you DCHECK/NOTREACHED, don't try to recover")

[pastarmovj, 2016/12/05 08:40:10]

Done.

+  // this happening most probably you are using SYSLOG before you called
+  // SetEventSourceName.
+  if (g_event_source_name == nullptr) {
+    stream() << " !!EVENTLOG SOURCE NAME NOT SET!!";
+    return;
+  }
+  HANDLE event_log_handle =
+      RegisterEventSourceA(NULL, g_event_source_name->c_str());
   if (event_log_handle == NULL) {
     stream() << " !!NOT ADDED TO EVENTLOG!!";
     return;
   }
 
+  base::ScopedClosureRunner auto_deregister(
+      base::Bind(base::IgnoreResult(&DeregisterEventSource), event_log_handle));
   std::string message(log_message_.str());
   WORD log_type = EVENTLOG_ERROR_TYPE;
   switch (log_message_.severity()) {
@@ -57,7 +81,6 @@ EventLogMessage::~EventLogMessage() {
                     MSG_LOG_MESSAGE, NULL, 1, 0, strings, NULL)) {
     stream() << " !!NOT ADDED TO EVENTLOG!!";
   }
-  DeregisterEventSource(event_log_handle);
 #elif defined(OS_LINUX)
   const char kEventSource[] = "chrome";
   openlog(kEventSource, LOG_NOWAIT | LOG_PID, LOG_USER);