--- a/xpcom/base/nsQueryObject.h
+++ b/xpcom/base/nsQueryObject.h
@@ -10,17 +10,17 @@
 #include "mozilla/Attributes.h"
 
 #include "nsCOMPtr.h"
 #include "nsRefPtr.h"
 
 /*****************************************************************************/
 
 template<class T>
-class MOZ_STACK_CLASS nsQueryObject : public nsCOMPtr_helper
+class MOZ_STACK_CLASS nsQueryObject final : public nsCOMPtr_helper
 {
 public:
   explicit nsQueryObject(T* aRawPtr)
     : mRawPtr(aRawPtr)
   {
   }
 
   virtual nsresult NS_FASTCALL operator()(const nsIID& aIID,
@@ -30,17 +30,17 @@ public:
                               : NS_ERROR_NULL_POINTER;
     return status;
   }
 private:
   T* MOZ_NON_OWNING_REF mRawPtr;
 };
 
 template<class T>
-class MOZ_STACK_CLASS nsQueryObjectWithError : public nsCOMPtr_helper
+class MOZ_STACK_CLASS nsQueryObjectWithError final : public nsCOMPtr_helper
 {
 public:
   nsQueryObjectWithError(T* aRawPtr, nsresult* aErrorPtr)
     : mRawPtr(aRawPtr), mErrorPtr(aErrorPtr)
   {
   }
 
   virtual nsresult NS_FASTCALL operator()(const nsIID& aIID,

--- a/xpcom/glue/nsArrayUtils.h
+++ b/xpcom/glue/nsArrayUtils.h
@@ -6,17 +6,17 @@
 
 #ifndef nsArrayUtils_h__
 #define nsArrayUtils_h__
 
 #include "nsCOMPtr.h"
 #include "nsIArray.h"
 
 // helper class for do_QueryElementAt
-class MOZ_STACK_CLASS nsQueryArrayElementAt : public nsCOMPtr_helper
+class MOZ_STACK_CLASS nsQueryArrayElementAt final : public nsCOMPtr_helper
 {
 public:
   nsQueryArrayElementAt(nsIArray* aArray, uint32_t aIndex,
                         nsresult* aErrorPtr)
     : mArray(aArray)
     , mIndex(aIndex)
     , mErrorPtr(aErrorPtr)
   {

--- a/xpcom/glue/nsCOMPtr.h
+++ b/xpcom/glue/nsCOMPtr.h
@@ -164,17 +164,17 @@ public:
   nsQueryInterface(nsISupports* aRawPtr) : mRawPtr(aRawPtr) {}
 
   nsresult NS_FASTCALL operator()(const nsIID& aIID, void**) const;
 
 private:
   nsISupports* MOZ_OWNING_REF mRawPtr;
 };
 
-class nsQueryInterfaceWithError
+class nsQueryInterfaceWithError final
 {
 public:
   nsQueryInterfaceWithError(nsISupports* aRawPtr, nsresult* aError)
     : mRawPtr(aRawPtr)
     , mErrorPtr(aError)
   {
   }
 
@@ -213,58 +213,58 @@ do_QueryInterface(already_AddRefed<T>&, 
   // This signature exists solely to _stop_ you from doing the bad thing.
   // Saying |do_QueryInterface()| on a pointer that is not otherwise owned by
   // someone else is an automatic leak. See bug 8221.
 }
 
 
 ////////////////////////////////////////////////////////////////////////////
 // Using servicemanager with COMPtrs
-class nsGetServiceByCID
+class nsGetServiceByCID final
 {
 public:
   explicit nsGetServiceByCID(const nsCID& aCID) : mCID(aCID) {}
 
   nsresult NS_FASTCALL operator()(const nsIID&, void**) const;
 
 private:
   const nsCID& mCID;
 };
 
-class nsGetServiceByCIDWithError
+class nsGetServiceByCIDWithError final
 {
 public:
   nsGetServiceByCIDWithError(const nsCID& aCID, nsresult* aErrorPtr)
     : mCID(aCID)
     , mErrorPtr(aErrorPtr)
   {
   }
 
   nsresult NS_FASTCALL operator()(const nsIID&, void**) const;
 
 private:
   const nsCID& mCID;
   nsresult* mErrorPtr;
 };
 
-class nsGetServiceByContractID
+class nsGetServiceByContractID final
 {
 public:
   explicit nsGetServiceByContractID(const char* aContractID)
     : mContractID(aContractID)
   {
   }
 
   nsresult NS_FASTCALL operator()(const nsIID&, void**) const;
 
 private:
   const char* mContractID;
 };
 
-class nsGetServiceByContractIDWithError
+class nsGetServiceByContractIDWithError final
 {
 public:
   nsGetServiceByContractIDWithError(const char* aContractID, nsresult* aErrorPtr)
     : mContractID(aContractID)
     , mErrorPtr(aErrorPtr)
   {
   }
 

--- a/xpcom/glue/nsComponentManagerUtils.h
+++ b/xpcom/glue/nsComponentManagerUtils.h
@@ -21,17 +21,17 @@ nsresult CallCreateInstance(const char* 
 
 nsresult CallGetClassObject(const nsCID& aClass, const nsIID& aIID,
                             void** aResult);
 
 nsresult CallGetClassObject(const char* aContractID, const nsIID& aIID,
                             void** aResult);
 
 
-class MOZ_STACK_CLASS nsCreateInstanceByCID : public nsCOMPtr_helper
+class MOZ_STACK_CLASS nsCreateInstanceByCID final : public nsCOMPtr_helper
 {
 public:
   nsCreateInstanceByCID(const nsCID& aCID, nsISupports* aOuter,
                         nsresult* aErrorPtr)
     : mCID(aCID)
     , mOuter(aOuter)
     , mErrorPtr(aErrorPtr)
   {
@@ -41,17 +41,17 @@ public:
     override;
 
 private:
   const nsCID&    mCID;
   nsISupports* MOZ_NON_OWNING_REF mOuter;
   nsresult*       mErrorPtr;
 };
 
-class MOZ_STACK_CLASS nsCreateInstanceByContractID : public nsCOMPtr_helper
+class MOZ_STACK_CLASS nsCreateInstanceByContractID final : public nsCOMPtr_helper
 {
 public:
   nsCreateInstanceByContractID(const char* aContractID, nsISupports* aOuter,
                                nsresult* aErrorPtr)
     : mContractID(aContractID)
     , mOuter(aOuter)
     , mErrorPtr(aErrorPtr)
   {
@@ -60,17 +60,17 @@ public:
   virtual nsresult NS_FASTCALL operator()(const nsIID&, void**) const override;
 
 private:
   const char*   mContractID;
   nsISupports* MOZ_NON_OWNING_REF mOuter;
   nsresult*     mErrorPtr;
 };
 
-class MOZ_STACK_CLASS nsCreateInstanceFromFactory : public nsCOMPtr_helper
+class MOZ_STACK_CLASS nsCreateInstanceFromFactory final : public nsCOMPtr_helper
 {
 public:
   nsCreateInstanceFromFactory(nsIFactory* aFactory, nsISupports* aOuter,
                               nsresult* aErrorPtr)
     : mFactory(aFactory)
     , mOuter(aOuter)
     , mErrorPtr(aErrorPtr)
   {
@@ -119,33 +119,33 @@ do_CreateInstance(nsIFactory* aFactory, 
 inline const nsCreateInstanceFromFactory
 do_CreateInstance(nsIFactory* aFactory, nsISupports* aOuter,
                   nsresult* aError = 0)
 {
   return nsCreateInstanceFromFactory(aFactory, aOuter, aError);
 }
 
 
-class MOZ_STACK_CLASS nsGetClassObjectByCID : public nsCOMPtr_helper
+class MOZ_STACK_CLASS nsGetClassObjectByCID final : public nsCOMPtr_helper
 {
 public:
   nsGetClassObjectByCID(const nsCID& aCID, nsresult* aErrorPtr)
     : mCID(aCID)
     , mErrorPtr(aErrorPtr)
   {
   }
 
   virtual nsresult NS_FASTCALL operator()(const nsIID&, void**) const override;
 
 private:
   const nsCID&    mCID;
   nsresult*       mErrorPtr;
 };
 
-class MOZ_STACK_CLASS nsGetClassObjectByContractID : public nsCOMPtr_helper
+class MOZ_STACK_CLASS nsGetClassObjectByContractID final : public nsCOMPtr_helper
 {
 public:
   nsGetClassObjectByContractID(const char* aContractID, nsresult* aErrorPtr)
     : mContractID(aContractID)
     , mErrorPtr(aErrorPtr)
   {
   }
 

--- a/xpcom/glue/nsIInterfaceRequestorUtils.h
+++ b/xpcom/glue/nsIInterfaceRequestorUtils.h
@@ -17,17 +17,17 @@ CallGetInterface(T* aSource, Destination
 {
   NS_PRECONDITION(aSource, "null parameter");
   NS_PRECONDITION(aDestination, "null parameter");
 
   return aSource->GetInterface(NS_GET_TEMPLATE_IID(DestinationType),
                                reinterpret_cast<void**>(aDestination));
 }
 
-class MOZ_STACK_CLASS nsGetInterface : public nsCOMPtr_helper
+class MOZ_STACK_CLASS nsGetInterface final : public nsCOMPtr_helper
 {
 public:
   nsGetInterface(nsISupports* aSource, nsresult* aError)
     : mSource(aSource)
     , mErrorPtr(aError)
   {
   }
 

--- a/xpcom/glue/nsIWeakReferenceUtils.h
+++ b/xpcom/glue/nsIWeakReferenceUtils.h
@@ -25,17 +25,17 @@ CallQueryReferent(T* aSource, Destinatio
   NS_PRECONDITION(aSource, "null parameter");
   NS_PRECONDITION(aDestination, "null parameter");
 
   return aSource->QueryReferent(NS_GET_TEMPLATE_IID(DestinationType),
                                 reinterpret_cast<void**>(aDestination));
 }
 
 
-class MOZ_STACK_CLASS nsQueryReferent : public nsCOMPtr_helper
+class MOZ_STACK_CLASS nsQueryReferent final : public nsCOMPtr_helper
 {
 public:
   nsQueryReferent(nsIWeakReference* aWeakPtr, nsresult* aError)
     : mWeakPtr(aWeakPtr)
     , mErrorPtr(aError)
   {
   }
 

--- a/xpcom/glue/nsServiceManagerUtils.h
+++ b/xpcom/glue/nsServiceManagerUtils.h
@@ -29,17 +29,17 @@ do_GetService(const char* aContractID)
 }
 
 inline const nsGetServiceByContractIDWithError
 do_GetService(const char* aContractID, nsresult* aError)
 {
   return nsGetServiceByContractIDWithError(aContractID, aError);
 }
 
-class MOZ_STACK_CLASS nsGetServiceFromCategory : public nsCOMPtr_helper
+class MOZ_STACK_CLASS nsGetServiceFromCategory final : public nsCOMPtr_helper
 {
 public:
   nsGetServiceFromCategory(const char* aCategory, const char* aEntry,
                            nsresult* aErrorPtr)
     : mCategory(aCategory)
     , mEntry(aEntry)
     , mErrorPtr(aErrorPtr)
   {