--- a/accessible/generic/Accessible-inl.h
+++ b/accessible/generic/Accessible-inl.h
@@ -24,39 +24,57 @@ Accessible::Role()
   const nsRoleMapEntry* roleMapEntry = ARIARoleMap();
   if (!roleMapEntry || roleMapEntry->roleRule != kUseMapRole)
     return ARIATransformRole(NativeRole());
 
   return ARIATransformRole(roleMapEntry->role);
 }
 
 inline bool
+Accessible::HasARIARole() const
+{
+  return mRoleMapEntryIndex != aria::NO_ROLE_MAP_ENTRY_INDEX;
+}
+
+inline bool
 Accessible::IsARIARole(nsIAtom* aARIARole) const
 {
   const nsRoleMapEntry* roleMapEntry = ARIARoleMap();
   return roleMapEntry && roleMapEntry->Is(aARIARole);
 }
 
 inline bool
 Accessible::HasStrongARIARole() const
 {
   const nsRoleMapEntry* roleMapEntry = ARIARoleMap();
   return roleMapEntry && roleMapEntry->roleRule == kUseMapRole;
 }
 
+inline const nsRoleMapEntry*
+Accessible::ARIARoleMap() const
+{
+  return aria::GetRoleMapFromIndex(mRoleMapEntryIndex);
+}
+
 inline mozilla::a11y::role
 Accessible::ARIARole()
 {
   const nsRoleMapEntry* roleMapEntry = ARIARoleMap();
   if (!roleMapEntry || roleMapEntry->roleRule != kUseMapRole)
     return mozilla::a11y::roles::NOTHING;
 
   return ARIATransformRole(roleMapEntry->role);
 }
 
+inline void
+Accessible::SetRoleMapEntry(const nsRoleMapEntry* aRoleMapEntry)
+{
+  mRoleMapEntryIndex = aria::GetIndexFromRoleMap(aRoleMapEntry);
+}
+
 inline bool
 Accessible::IsSearchbox() const
 {
   const nsRoleMapEntry* roleMapEntry = ARIARoleMap();
   return (roleMapEntry && roleMapEntry->Is(nsGkAtoms::searchbox)) ||
     (mContent->IsHTMLElement(nsGkAtoms::input) &&
      mContent->AttrValueIs(kNameSpaceID_None, nsGkAtoms::type,
                            nsGkAtoms::textInputType, eCaseMatters));

--- a/accessible/generic/Accessible.cpp
+++ b/accessible/generic/Accessible.cpp
@@ -103,18 +103,18 @@ NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(
 NS_INTERFACE_MAP_END
 
 NS_IMPL_CYCLE_COLLECTING_ADDREF(Accessible)
 NS_IMPL_CYCLE_COLLECTING_RELEASE_WITH_DESTROY(Accessible, LastRelease())
 
 Accessible::Accessible(nsIContent* aContent, DocAccessible* aDoc) :
   mContent(aContent), mDoc(aDoc),
   mParent(nullptr), mIndexInParent(-1),
-  mStateFlags(0), mContextFlags(0), mType(0), mGenericTypes(0),
-  mRoleMapEntry(nullptr)
+  mRoleMapEntryIndex(aria::NO_ROLE_MAP_ENTRY_INDEX),
+  mStateFlags(0), mContextFlags(0), mType(0), mGenericTypes(0)
 {
   mBits.groupInfo = nullptr;
   mInt.mIndexOfEmbeddedChild = -1;
 }
 
 Accessible::~Accessible()
 {
   NS_ASSERTION(!mDoc, "LastRelease was never called!?!");

--- a/accessible/generic/Accessible.h
+++ b/accessible/generic/Accessible.h
@@ -225,24 +225,24 @@ public:
   /**
    * Return enumerated accessible role (see constants in Role.h).
    */
   mozilla::a11y::role Role();
 
   /**
    * Return true if ARIA role is specified on the element.
    */
-  bool HasARIARole() const { return mRoleMapEntry; }
+  bool HasARIARole() const;
   bool IsARIARole(nsIAtom* aARIARole) const;
   bool HasStrongARIARole() const;
 
   /**
    * Retrun ARIA role map if any.
    */
-  const nsRoleMapEntry* ARIARoleMap() const { return mRoleMapEntry; }
+  const nsRoleMapEntry* ARIARoleMap() const;
 
   /**
    * Return accessible role specified by ARIA (see constants in
    * roles).
    */
   mozilla::a11y::role ARIARole();
 
   /**
@@ -378,18 +378,17 @@ public:
   /**
    * Shutdown this accessible object.
    */
   virtual void Shutdown();
 
   /**
    * Set the ARIA role map entry for a new accessible.
    */
-  void SetRoleMapEntry(const nsRoleMapEntry* aRoleMapEntry)
-    { mRoleMapEntry = aRoleMapEntry; }
+  void SetRoleMapEntry(const nsRoleMapEntry* aRoleMapEntry);
 
   /**
    * Append/insert/remove a child. Return true if operation was successful.
    */
   bool AppendChild(Accessible* aChild)
     { return InsertChildAt(mChildren.Length(), aChild); }
   virtual bool InsertChildAt(uint32_t aIndex, Accessible* aChild);
 
@@ -1115,16 +1114,22 @@ protected:
   int32_t mIndexInParent;
 
   static const uint8_t kStateFlagsBits = 13;
   static const uint8_t kContextFlagsBits = 3;
   static const uint8_t kTypeBits = 6;
   static const uint8_t kGenericTypesBits = 16;
 
   /**
+   * Non-NO_ROLE_MAP_ENTRY_INDEX indicates author-supplied role;
+   * possibly state & value as well
+   */
+  uint8_t mRoleMapEntryIndex;
+
+  /**
    * Keep in sync with StateFlags, ContextFlags, and AccTypes.
    */
   uint32_t mStateFlags : kStateFlagsBits;
   uint32_t mContextFlags : kContextFlagsBits;
   uint32_t mType : kTypeBits;
   uint32_t mGenericTypes : kGenericTypesBits;
 
   void StaticAsserts() const;
@@ -1149,21 +1154,16 @@ protected:
 
   union
   {
     AccGroupInfo* groupInfo;
     ProxyAccessible* proxy;
   } mBits;
   friend class AccGroupInfo;
 
-  /**
-   * Non-null indicates author-supplied role; possibly state & value as well
-   */
-  const nsRoleMapEntry* mRoleMapEntry;
-
 private:
   Accessible() = delete;
   Accessible(const Accessible&) = delete;
   Accessible& operator =(const Accessible&) = delete;
 
 };
 
 NS_DEFINE_STATIC_IID_ACCESSOR(Accessible,