diff -r 000000000000 -r 6474c204b198 layout/mathml/nsMathMLmphantomFrame.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/layout/mathml/nsMathMLmphantomFrame.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,46 @@
+/* -*- 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/. */
+
+#ifndef nsMathMLmphantomFrame_h___
+#define nsMathMLmphantomFrame_h___
+
+#include "mozilla/Attributes.h"
+#include "nsMathMLContainerFrame.h"
+
+//
+// <mphantom> -- make content invisible but preserve its size
+//
+
+class nsMathMLmphantomFrame : public nsMathMLContainerFrame {
+public:
+  NS_DECL_FRAMEARENA_HELPERS
+
+  friend nsIFrame* NS_NewMathMLmphantomFrame(nsIPresShell* aPresShell, nsStyleContext* aContext);
+
+  NS_IMETHOD
+  InheritAutomaticData(nsIFrame* aParent) MOZ_OVERRIDE;
+
+  NS_IMETHOD
+  TransmitAutomaticData() MOZ_OVERRIDE {
+    return TransmitAutomaticDataForMrowLikeElement();
+  }
+
+  virtual void BuildDisplayList(nsDisplayListBuilder*   aBuilder,
+                                const nsRect&           aDirtyRect,
+                                const nsDisplayListSet& aLists) MOZ_OVERRIDE {}
+
+  bool
+  IsMrowLike() MOZ_OVERRIDE {
+    return mFrames.FirstChild() != mFrames.LastChild() ||
+           !mFrames.FirstChild();
+  }
+
+protected:
+  nsMathMLmphantomFrame(nsStyleContext* aContext)
+    : nsMathMLContainerFrame(aContext) {}
+  virtual ~nsMathMLmphantomFrame();
+};
+
+#endif /* nsMathMLmphantomFrame_h___ */