diff -r 000000000000 -r 6474c204b198 layout/base/nsILayoutDebugger.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/layout/base/nsILayoutDebugger.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,47 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+/* XPCOM interface for layout-debug extension to reach layout internals */
+
+#ifndef nsILayoutDebugger_h___
+#define nsILayoutDebugger_h___
+
+#include "nsISupports.h"
+
+class nsIDocument;
+class nsIPresShell;
+
+/* a6cf90f8-15b3-11d2-932e-00805f8add32 */
+#define NS_ILAYOUT_DEBUGGER_IID \
+ { 0xa6cf90f8, 0x15b3, 0x11d2,{0x93, 0x2e, 0x00, 0x80, 0x5f, 0x8a, 0xdd, 0x32}}
+
+/**
+ * API for access and control of layout debugging
+ */
+class nsILayoutDebugger : public nsISupports {
+public:
+  NS_DECLARE_STATIC_IID_ACCESSOR(NS_ILAYOUT_DEBUGGER_IID)
+
+  NS_IMETHOD SetShowFrameBorders(bool aEnable) = 0;
+
+  NS_IMETHOD GetShowFrameBorders(bool* aResult) = 0;
+
+  NS_IMETHOD SetShowEventTargetFrameBorder(bool aEnable) = 0;
+
+  NS_IMETHOD GetShowEventTargetFrameBorder(bool* aResult) = 0;
+
+  NS_IMETHOD GetContentSize(nsIDocument* aDocument,
+                            int32_t* aSizeInBytesResult) = 0;
+
+  NS_IMETHOD GetFrameSize(nsIPresShell* aPresentation,
+                          int32_t* aSizeInBytesResult) = 0;
+
+  NS_IMETHOD GetStyleSize(nsIPresShell* aPresentation,
+                          int32_t* aSizeInBytesResult) = 0;
+};
+
+NS_DEFINE_STATIC_IID_ACCESSOR(nsILayoutDebugger, NS_ILAYOUT_DEBUGGER_IID)
+
+#endif /* nsILayoutDebugger_h___ */