Don't evaluate args to LOG(INFO) and LOG(WARNING) in release builds.

base/logging.cc

 // Copyright (c) 2012 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 "base/logging.h"
 
 #if defined(OS_WIN)
 #include <io.h>
 #include <windows.h>
 #include "base/files/file_path.h"
@@ skipping 372 matching lines @@
 }
 
 void SetMinLogLevel(int level) {
   g_min_log_level = std::min(LOG_FATAL, level);
 }
 
 int GetMinLogLevel() {
   return g_min_log_level;
 }
 
+bool ShouldCreateLogMessage(int severity) {
+  if (severity < g_min_log_level)
+    return false;
+
+  // These are the cases for which ~LogMessage does something.
+  return g_logging_destination != LOG_NONE || log_message_handler ||
+         severity >= kAlwaysPrintErrorLevel;

[brettw, 2015/12/03 23:52:14]

Do ew need the kAlwaysPrintErrorLevel check here? If there is no destinatoin and
no message handler, can even LOG_FATAL go anywhere? If this is needed, we should
mention in the comment why.

[skobes, 2015/12/03 23:57:26]

Yeah, ~LogMessage writes to stderr if severity_ >= kAlwaysPrintErrorLevel, even
when g_logging_destination is LOG_NONE.

I tried to capture this in the comment... is there another way of wording it
that you'd prefer?

+}
+
 int GetVlogVerbosity() {
   return std::max(-1, LOG_INFO - GetMinLogLevel());
 }
 
 int GetVlogLevelHelper(const char* file, size_t N) {
   DCHECK_GT(N, 0U);
   // Note: |g_vlog_info| may change on a different thread during startup
   // (but will always be valid or nullptr).
   VlogInfo* vlog_info = g_vlog_info;
   return vlog_info ?
@@ skipping 491 matching lines @@
 BASE_EXPORT void LogErrorNotReached(const char* file, int line) {
   LogMessage(file, line, LOG_ERROR).stream()
       << "NOTREACHED() hit.";
 }
 
 }  // namespace logging
 
 std::ostream& std::operator<<(std::ostream& out, const wchar_t* wstr) {
   return out << base::WideToUTF8(wstr);
 }