diff -r 000000000000 -r 6474c204b198 js/xpconnect/src/XPCLog.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/xpconnect/src/XPCLog.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,98 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* vim: set ts=8 sts=4 et sw=4 tw=99: */
+/* 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/. */
+
+/* Debug Logging support. */
+
+#include "XPCLog.h"
+#include "prlog.h"
+#include "prprf.h"
+#include "mozilla/mozalloc.h"
+#include "mozilla/NullPtr.h"
+#include <string.h>
+#include <stdarg.h>
+
+// this all only works for DEBUG...
+#ifdef DEBUG
+
+#define SPACE_COUNT     200
+#define LINE_LEN        200
+#define INDENT_FACTOR   2
+
+#define CAN_RUN (g_InitState == 1 || (g_InitState == 0 && Init()))
+
+static char*    g_Spaces;
+static int      g_InitState = 0;
+static int      g_Indent = 0;
+static PRLogModuleInfo* g_LogMod = nullptr;
+
+static bool Init()
+{
+    g_LogMod = PR_NewLogModule("xpclog");
+    g_Spaces = new char[SPACE_COUNT+1];
+    if (!g_LogMod || !g_Spaces || !PR_LOG_TEST(g_LogMod,1)) {
+        g_InitState = 1;
+        XPC_Log_Finish();
+        return false;
+    }
+    memset(g_Spaces, ' ', SPACE_COUNT);
+    g_Spaces[SPACE_COUNT] = 0;
+    g_InitState = 1;
+    return true;
+}
+
+void
+XPC_Log_Finish()
+{
+    if (g_InitState == 1) {
+        delete [] g_Spaces;
+        // we'd like to properly cleanup the LogModule, but nspr owns that
+        g_LogMod = nullptr;
+    }
+    g_InitState = -1;
+}
+
+void
+XPC_Log_print(const char *fmt, ...)
+{
+    va_list ap;
+    char line[LINE_LEN];
+
+    va_start(ap, fmt);
+    PR_vsnprintf(line, sizeof(line)-1, fmt, ap);
+    va_end(ap);
+    if (g_Indent)
+        PR_LogPrint("%s%s",g_Spaces+SPACE_COUNT-(INDENT_FACTOR*g_Indent),line);
+    else
+        PR_LogPrint("%s",line);
+}
+
+bool
+XPC_Log_Check(int i)
+{
+    return CAN_RUN && PR_LOG_TEST(g_LogMod,1);
+}
+
+void
+XPC_Log_Indent()
+{
+    if (INDENT_FACTOR*(++g_Indent) > SPACE_COUNT)
+        g_Indent-- ;
+}
+
+void
+XPC_Log_Outdent()
+{
+    if (--g_Indent < 0)
+        g_Indent++;
+}
+
+void
+XPC_Log_Clear_Indent()
+{
+    g_Indent = 0;
+}
+
+#endif