Made logging macros evaluate its stream arguments lazily.

base/logging.cc

 // Copyright (c) 2010 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>
 typedef HANDLE FileHandle;
@@ skipping 543 matching lines @@
   }
   if (log_tickcount)
     stream_ << TickCount() << ':';
   stream_ << log_severity_names[severity_] << ":" << file <<
              "(" << line << ")] ";
 
   message_start_ = stream_.tellp();
 }
 
 LogMessage::~LogMessage() {
-  // TODO(brettw) modify the macros so that nothing is executed when the log
-  // level is too high.
+  // The macros in logging.h should already avoid creating LogMessages
+  // when this holds, but it's possible that users create LogMessages
+  // directly (e.g., using LOG_STREAM() directly).
   if (severity_ < min_log_level)
     return;
 
 #ifndef NDEBUG
   if (severity_ == LOG_FATAL) {
     // Include a stack trace on a fatal.
     StackTrace trace;
     stream_ << std::endl;  // Newline to separate from log message.
     trace.OutputToStream(&stream_);
   }
@@ skipping 206 matching lines @@
 
   if (level == LOG_FATAL)
     DebugUtil::BreakDebugger();
 }
 
 }  // namespace logging
 
 std::ostream& operator<<(std::ostream& out, const wchar_t* wstr) {
   return out << WideToUTF8(std::wstring(wstr));
 }