diff -r 000000000000 -r 6474c204b198 layout/tools/layout-debug/src/nsLayoutDebugCLH.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/layout/tools/layout-debug/src/nsLayoutDebugCLH.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,84 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+// vim:cindent:tabstop=4:expandtab:shiftwidth=4:
+/* 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/. */
+
+#include "nsLayoutDebugCLH.h"
+#include "nsString.h"
+#include "plstr.h"
+#include "nsCOMPtr.h"
+#include "nsIWindowWatcher.h"
+#include "nsIServiceManager.h"
+#include "nsIDOMWindow.h"
+#include "nsISupportsArray.h"
+#include "nsISupportsPrimitives.h"
+#include "nsICommandLine.h"
+
+nsLayoutDebugCLH::nsLayoutDebugCLH()
+{
+}
+
+nsLayoutDebugCLH::~nsLayoutDebugCLH()
+{
+}
+
+NS_IMPL_ISUPPORTS(nsLayoutDebugCLH, ICOMMANDLINEHANDLER)
+
+NS_IMETHODIMP
+nsLayoutDebugCLH::Handle(nsICommandLine* aCmdLine)
+{
+    nsresult rv;
+
+    int32_t idx;
+    rv = aCmdLine->FindFlag(NS_LITERAL_STRING("layoutdebug"), false, &idx);
+    NS_ENSURE_SUCCESS(rv, rv);
+    if (idx < 0)
+      return NS_OK;
+
+    int32_t length;
+    aCmdLine->GetLength(&length);
+
+    nsAutoString url;
+    if (idx + 1 < length) {
+        rv = aCmdLine->GetArgument(idx + 1, url);
+        NS_ENSURE_SUCCESS(rv, rv);
+        if (!url.IsEmpty() && url.CharAt(0) == '-')
+            url.Truncate();
+    }
+
+    aCmdLine->RemoveArguments(idx, idx + !url.IsEmpty());
+
+    nsCOMPtr<nsISupportsArray> argsArray =
+        do_CreateInstance(NS_SUPPORTSARRAY_CONTRACTID, &rv);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    if (!url.IsEmpty())
+    {
+        nsCOMPtr<nsISupportsString> scriptableURL =
+            do_CreateInstance(NS_SUPPORTS_STRING_CONTRACTID);
+        NS_ENSURE_TRUE(scriptableURL, NS_ERROR_FAILURE);
+  
+        scriptableURL->SetData(url);
+        argsArray->AppendElement(scriptableURL);
+    }
+
+    nsCOMPtr<nsIWindowWatcher> wwatch =
+        do_GetService(NS_WINDOWWATCHER_CONTRACTID);
+    NS_ENSURE_TRUE(wwatch, NS_ERROR_FAILURE);
+
+    nsCOMPtr<nsIDOMWindow> opened;
+    wwatch->OpenWindow(nullptr, "chrome://layoutdebug/content/",
+                       "_blank", "chrome,dialog=no,all", argsArray,
+                       getter_AddRefs(opened));
+    aCmdLine->SetPreventDefault(true);
+    return NS_OK;
+}
+
+NS_IMETHODIMP
+nsLayoutDebugCLH::GetHelpInfo(nsACString& aResult)
+{
+    aResult.Assign(NS_LITERAL_CSTRING("  -layoutdebug [<url>] Start with Layout Debugger\n"));
+    return NS_OK;
+}
+