diff -r 000000000000 -r 6474c204b198 layout/mathml/nsMathMLmrowFrame.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/layout/mathml/nsMathMLmrowFrame.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,69 @@
+/* -*- 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/. */
+
+#include "nsMathMLmrowFrame.h"
+#include "mozilla/gfx/2D.h"
+
+//
+// <mrow> -- horizontally group any number of subexpressions - implementation
+//
+
+nsIFrame*
+NS_NewMathMLmrowFrame(nsIPresShell* aPresShell, nsStyleContext* aContext)
+{
+  return new (aPresShell) nsMathMLmrowFrame(aContext);
+}
+
+NS_IMPL_FRAMEARENA_HELPERS(nsMathMLmrowFrame)
+
+nsMathMLmrowFrame::~nsMathMLmrowFrame()
+{
+}
+
+NS_IMETHODIMP
+nsMathMLmrowFrame::InheritAutomaticData(nsIFrame* aParent)
+{
+  // let the base class get the default from our parent
+  nsMathMLContainerFrame::InheritAutomaticData(aParent);
+
+  mPresentationData.flags |= NS_MATHML_STRETCH_ALL_CHILDREN_VERTICALLY;
+
+  return NS_OK;
+}
+
+nsresult
+nsMathMLmrowFrame::AttributeChanged(int32_t  aNameSpaceID,
+                                    nsIAtom* aAttribute,
+                                    int32_t  aModType)
+{
+  // Special for <mtable>: In the frame construction code, we also use
+  // this frame class as a wrapper for mtable. Hence, we should pass the
+  // notification to the real mtable
+  if (mContent->Tag() == nsGkAtoms::mtable_) {
+    nsIFrame* frame = mFrames.FirstChild();
+    for ( ; frame; frame = frame->GetFirstPrincipalChild()) {
+      // drill down to the real mtable
+      if (frame->GetType() == nsGkAtoms::tableOuterFrame)
+        return frame->AttributeChanged(aNameSpaceID, aAttribute, aModType);
+    }
+    NS_NOTREACHED("mtable wrapper without the real table frame");
+  }
+
+  return nsMathMLContainerFrame::AttributeChanged(aNameSpaceID, aAttribute, aModType);
+}
+
+/* virtual */ eMathMLFrameType
+nsMathMLmrowFrame::GetMathMLFrameType()
+{
+  if (!IsMrowLike()) {
+    nsIMathMLFrame* child = do_QueryFrame(mFrames.FirstChild());
+    if (child) {
+      // We only have one child, so we return the frame type of that child as if
+      // we didn't exist.
+      return child->GetMathMLFrameType();
+    }
+  }
+  return nsMathMLFrame::GetMathMLFrameType();
+}