--- a/xpcom/reflect/xptinfo/xptiInterfaceInfo.cpp
+++ b/xpcom/reflect/xptinfo/xptiInterfaceInfo.cpp
@@ -580,70 +580,31 @@ xptiInterfaceInfo::BuildParent()
                  mEntry->Parent(),
                "bad BuildParent call");
   mParent = mEntry->Parent()->InterfaceInfo();
   return true;
 }
 
 /***************************************************************************/
 
-NS_IMPL_QUERY_INTERFACE(xptiInterfaceInfo, nsIInterfaceInfo)
+NS_IMPL_ISUPPORTS(xptiInterfaceInfo, nsIInterfaceInfo)
 
-xptiInterfaceInfo::xptiInterfaceInfo(xptiInterfaceEntry* entry)
-  : mEntry(entry)
+xptiInterfaceInfo::xptiInterfaceInfo(xptiInterfaceEntry* aEntry)
+  : mEntry(aEntry)
 {
+  MOZ_ASSERT(aEntry);
 }
 
 xptiInterfaceInfo::~xptiInterfaceInfo()
 {
-  NS_ASSERTION(!mEntry, "bad state in dtor");
+  if (mEntry) {
+    mEntry->InterfaceInfoDeathNotification();
+  }
 }
 
 void
 xptiInterfaceInfo::Invalidate()
 {
   mParent = nullptr;
   mEntry = nullptr;
 }
 
-MozExternalRefCountType
-xptiInterfaceInfo::AddRef(void)
-{
-  nsrefcnt cnt = ++mRefCnt;
-  NS_LOG_ADDREF(this, cnt, "xptiInterfaceInfo", sizeof(*this));
-  return cnt;
-}
-
-MozExternalRefCountType
-xptiInterfaceInfo::Release(void)
-{
-  xptiInterfaceEntry* entry = mEntry;
-  nsrefcnt cnt = --mRefCnt;
-  NS_LOG_RELEASE(this, cnt, "xptiInterfaceInfo");
-  if (!cnt) {
-    // If InterfaceInfo added and *released* a reference before we
-    // acquired the monitor then 'this' might already be dead. In that
-    // case we would not want to try to access any instance data. We
-    // would want to bail immediately. If 'this' is already dead then the
-    // entry will no longer have a pointer to 'this'. So, we can protect
-    // ourselves from danger without more aggressive locking.
-    if (entry && !entry->InterfaceInfoEquals(this)) {
-      return 0;
-    }
-
-    // If InterfaceInfo added a reference before we acquired the monitor
-    // then we want to bail out of here without destorying the object.
-    if (mRefCnt) {
-      return 1;
-    }
-
-    if (mEntry) {
-      mEntry->InterfaceInfoDeathNotification();
-      mEntry = nullptr;
-    }
-
-    delete this;
-    return 0;
-  }
-  return cnt;
-}
-
 /***************************************************************************/

--- a/xpcom/reflect/xptinfo/xptiprivate.h
+++ b/xpcom/reflect/xptinfo/xptiprivate.h
@@ -214,20 +214,16 @@ public:
   bool GetHasNotXPCOMFlag() const { return mFlags.GetFlagBit(HASNOTXPCOM); }
 
   const nsID* GetTheIID() const { return &mIID; }
   const char* GetTheName() const { return mName; }
 
   bool EnsureResolved() { return IsFullyResolved() ? true : Resolve(); }
 
   already_AddRefed<xptiInterfaceInfo> InterfaceInfo();
-  bool InterfaceInfoEquals(const xptiInterfaceInfo* info) const
-  {
-    return info == mInfo;
-  }
 
   void InvalidateInterfaceInfo();
   void InterfaceInfoDeathNotification() { mInfo = nullptr; }
 
   xptiInterfaceEntry* Parent() const
   {
     NS_ASSERTION(IsFullyResolved(), "Parent() called while not resolved?");
     return mParent;