diff -r 000000000000 -r 6474c204b198 dom/smil/nsSMILSetAnimationFunction.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/smil/nsSMILSetAnimationFunction.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,100 @@
+/* -*- 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 "nsSMILSetAnimationFunction.h"
+
+inline bool
+nsSMILSetAnimationFunction::IsDisallowedAttribute(
+    const nsIAtom* aAttribute) const
+{
+  //
+  // A <set> element is similar to <animate> but lacks:
+  //   AnimationValue.attrib(calcMode, values, keyTimes, keySplines, from, to,
+  //                         by) -- BUT has 'to'
+  //   AnimationAddition.attrib(additive, accumulate)
+  //
+  if (aAttribute == nsGkAtoms::calcMode ||
+      aAttribute == nsGkAtoms::values ||
+      aAttribute == nsGkAtoms::keyTimes ||
+      aAttribute == nsGkAtoms::keySplines ||
+      aAttribute == nsGkAtoms::from ||
+      aAttribute == nsGkAtoms::by ||
+      aAttribute == nsGkAtoms::additive ||
+      aAttribute == nsGkAtoms::accumulate) {
+    return true;
+  }
+
+  return false;
+}
+
+bool
+nsSMILSetAnimationFunction::SetAttr(nsIAtom* aAttribute,
+                                    const nsAString& aValue,
+                                    nsAttrValue& aResult,
+                                    nsresult* aParseResult)
+{
+  if (IsDisallowedAttribute(aAttribute)) {
+    aResult.SetTo(aValue);
+    if (aParseResult) {
+      // SMILANIM 4.2 says:
+      //
+      //   The additive and accumulate attributes are not allowed, and will be
+      //   ignored if specified.
+      //
+      // So at least for those two attributes we shouldn't report an error even
+      // if they're present. For now we'll also just silently ignore other
+      // attribute types too.
+      *aParseResult = NS_OK;
+    }
+    return true;
+  }
+
+  return nsSMILAnimationFunction::SetAttr(aAttribute, aValue,
+                                          aResult, aParseResult);
+}
+
+bool
+nsSMILSetAnimationFunction::UnsetAttr(nsIAtom* aAttribute)
+{
+  if (IsDisallowedAttribute(aAttribute)) {
+    return true;
+  }
+
+  return nsSMILAnimationFunction::UnsetAttr(aAttribute);
+}
+
+bool
+nsSMILSetAnimationFunction::HasAttr(nsIAtom* aAttName) const
+{
+  if (IsDisallowedAttribute(aAttName))
+    return false;
+
+  return nsSMILAnimationFunction::HasAttr(aAttName);
+}
+
+const nsAttrValue*
+nsSMILSetAnimationFunction::GetAttr(nsIAtom* aAttName) const
+{
+  if (IsDisallowedAttribute(aAttName))
+    return nullptr;
+
+  return nsSMILAnimationFunction::GetAttr(aAttName);
+}
+
+bool
+nsSMILSetAnimationFunction::GetAttr(nsIAtom* aAttName,
+                                    nsAString& aResult) const
+{
+  if (IsDisallowedAttribute(aAttName))
+    return false;
+
+  return nsSMILAnimationFunction::GetAttr(aAttName, aResult);
+}
+
+bool
+nsSMILSetAnimationFunction::WillReplace() const
+{
+  return true;
+}