diff -r 000000000000 -r 6474c204b198 dom/smil/nsSMILTargetIdentifier.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/smil/nsSMILTargetIdentifier.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,86 @@
+/* -*- 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 NS_SMILTARGETIDENTIFIER_H_
+#define NS_SMILTARGETIDENTIFIER_H_
+
+#include "mozilla/dom/Element.h"
+#include "nsAutoPtr.h"
+
+/**
+ * Struct: nsSMILTargetIdentifier
+ *
+ * Tuple of: { Animated Element, Attribute Name, Attribute Type (CSS vs. XML) }
+ *
+ * Used in nsSMILAnimationController as hash key for mapping an animation
+ * target to the nsSMILCompositor for that target.
+ *
+ * NOTE: Need a nsRefPtr for the element & attribute name, because
+ * nsSMILAnimationController retain its hash table for one sample into the
+ * future, and we need to make sure their target isn't deleted in that time.
+ */
+
+struct nsSMILTargetIdentifier
+{
+  nsSMILTargetIdentifier()
+    : mElement(nullptr), mAttributeName(nullptr),
+      mAttributeNamespaceID(kNameSpaceID_Unknown), mIsCSS(false) {}
+
+  inline bool Equals(const nsSMILTargetIdentifier& aOther) const
+  {
+    return (aOther.mElement              == mElement &&
+            aOther.mAttributeName        == mAttributeName &&
+            aOther.mAttributeNamespaceID == mAttributeNamespaceID &&
+            aOther.mIsCSS                == mIsCSS);
+  }
+
+  nsRefPtr<mozilla::dom::Element> mElement;
+  nsRefPtr<nsIAtom>    mAttributeName;
+  int32_t              mAttributeNamespaceID;
+  bool                 mIsCSS;
+};
+
+/**
+ * Class: nsSMILWeakTargetIdentifier
+ *
+ * Version of the above struct that uses non-owning pointers.  These are kept
+ * private, to ensure that they aren't ever dereferenced (or used at all,
+ * outside of Equals()).
+ *
+ * This is solely for comparisons to determine if a target has changed
+ * from one sample to the next.
+ */
+class nsSMILWeakTargetIdentifier
+{
+public:
+  // Trivial constructor
+  nsSMILWeakTargetIdentifier()
+    : mElement(nullptr), mAttributeName(nullptr), mIsCSS(false) {}
+
+  // Allow us to update a weak identifier to match a given non-weak identifier
+  nsSMILWeakTargetIdentifier&
+    operator=(const nsSMILTargetIdentifier& aOther)
+  {
+    mElement = aOther.mElement;
+    mAttributeName = aOther.mAttributeName;
+    mIsCSS = aOther.mIsCSS;
+    return *this;
+  }
+
+  // Allow for comparison vs. non-weak identifier
+  inline bool Equals(const nsSMILTargetIdentifier& aOther) const
+  {
+    return (aOther.mElement       == mElement &&
+            aOther.mAttributeName == mAttributeName &&
+            aOther.mIsCSS         == mIsCSS);
+  }
+
+private:
+  const nsIContent* mElement;
+  const nsIAtom*    mAttributeName;
+  bool              mIsCSS;
+};
+
+#endif // NS_SMILTARGETIDENTIFIER_H_