diff -r 000000000000 -r 6474c204b198 toolkit/mozapps/update/common/updatelogging.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/mozapps/update/common/updatelogging.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,82 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#if defined(XP_WIN)
+#include <windows.h>
+#endif
+
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdarg.h>
+
+#include "updatelogging.h"
+
+UpdateLog::UpdateLog() : logFP(nullptr)
+{
+}
+
+void UpdateLog::Init(NS_tchar* sourcePath,
+                     const NS_tchar* fileName,
+                     const NS_tchar* alternateFileName,
+                     bool append)
+{
+  if (logFP)
+    return;
+
+  this->sourcePath = sourcePath;
+  NS_tchar logFile[MAXPATHLEN];
+  NS_tsnprintf(logFile, sizeof(logFile)/sizeof(logFile[0]),
+    NS_T("%s/%s"), sourcePath, fileName);
+
+  if (alternateFileName && NS_taccess(logFile, F_OK)) {
+    NS_tsnprintf(logFile, sizeof(logFile)/sizeof(logFile[0]),
+      NS_T("%s/%s"), sourcePath, alternateFileName);
+  }
+
+  logFP = NS_tfopen(logFile, append ? NS_T("a") : NS_T("w"));
+}
+
+void UpdateLog::Finish()
+{
+  if (!logFP)
+    return;
+
+  fclose(logFP);
+  logFP = nullptr;
+}
+
+void UpdateLog::Flush()
+{
+  if (!logFP)
+    return;
+
+  fflush(logFP);
+}
+
+void UpdateLog::Printf(const char *fmt, ... )
+{
+  if (!logFP)
+    return;
+
+  va_list ap;
+  va_start(ap, fmt);
+  vfprintf(logFP, fmt, ap);
+  fprintf(logFP, "\n");
+  va_end(ap);
+}
+
+void UpdateLog::WarnPrintf(const char *fmt, ... )
+{
+  if (!logFP)
+    return;
+
+  va_list ap;
+  va_start(ap, fmt);
+  fprintf(logFP, "*** Warning: ");
+  vfprintf(logFP, fmt, ap);
+  fprintf(logFP, "***\n");
+  va_end(ap);
+}