diff --git a/toolkit/components/autocomplete/nsAutoCompleteSimpleResult.h b/toolkit/components/autocomplete/nsAutoCompleteSimpleResult.h
index 4d67516d0986..dbaab577829e 100644
--- a/toolkit/components/autocomplete/nsAutoCompleteSimpleResult.h
+++ b/toolkit/components/autocomplete/nsAutoCompleteSimpleResult.h
@@ -12,8 +12,9 @@
 #include "prtypes.h"
 #include "nsCOMPtr.h"
 #include "nsTArray.h"
+#include "mozilla/Attributes.h"
 
-class nsAutoCompleteSimpleResult : public nsIAutoCompleteSimpleResult
+class nsAutoCompleteSimpleResult MOZ_FINAL : public nsIAutoCompleteSimpleResult
 {
 public:
   nsAutoCompleteSimpleResult();
diff --git a/toolkit/components/commandlines/nsCommandLine.cpp b/toolkit/components/commandlines/nsCommandLine.cpp
index 816b710907b8..5e9e08aef9aa 100644
--- a/toolkit/components/commandlines/nsCommandLine.cpp
+++ b/toolkit/components/commandlines/nsCommandLine.cpp
@@ -24,6 +24,7 @@
 #include "nsTextFormatter.h"
 #include "nsXPCOMCID.h"
 #include "plstr.h"
+#include "mozilla/Attributes.h"
 
 #ifdef MOZ_WIDGET_COCOA
 #include <CoreFoundation/CoreFoundation.h>
@@ -44,7 +45,7 @@
 #define NS_COMMANDLINE_CID \
   { 0x23bcc750, 0xdc20, 0x460b, { 0xb2, 0xd4, 0x74, 0xd8, 0xf5, 0x8d, 0x36, 0x15 } }
 
-class nsCommandLine : public nsICommandLineRunner
+class nsCommandLine MOZ_FINAL : public nsICommandLineRunner
 {
 public:
   NS_DECL_ISUPPORTS
diff --git a/toolkit/components/ctypes/ctypes.h b/toolkit/components/ctypes/ctypes.h
index c0b7d4a8b7a9..f02902bc4113 100644
--- a/toolkit/components/ctypes/ctypes.h
+++ b/toolkit/components/ctypes/ctypes.h
@@ -7,11 +7,12 @@
 #define COMPONENTS_CTYPES_H
 
 #include "nsIXPCScriptable.h"
+#include "mozilla/Attributes.h"
 
 namespace mozilla {
 namespace ctypes {
 
-class Module : public nsIXPCScriptable
+class Module MOZ_FINAL : public nsIXPCScriptable
 {
 public:
   NS_DECL_ISUPPORTS
diff --git a/toolkit/components/perf/PerfMeasurement.h b/toolkit/components/perf/PerfMeasurement.h
index 659ea1ad18b3..a3230f7f0c77 100644
--- a/toolkit/components/perf/PerfMeasurement.h
+++ b/toolkit/components/perf/PerfMeasurement.h
@@ -7,11 +7,12 @@
 #define COMPONENTS_PERFMEASUREMENT_H
 
 #include "nsIXPCScriptable.h"
+#include "mozilla/Attributes.h"
 
 namespace mozilla {
 namespace jsperf {
 
-class Module : public nsIXPCScriptable
+class Module MOZ_FINAL : public nsIXPCScriptable
 {
 public:
   NS_DECL_ISUPPORTS
diff --git a/toolkit/components/reflect/reflect.h b/toolkit/components/reflect/reflect.h
index 181dc6bee520..8666444601b5 100644
--- a/toolkit/components/reflect/reflect.h
+++ b/toolkit/components/reflect/reflect.h
@@ -7,11 +7,12 @@
 #define COMPONENTS_REFLECT_H
 
 #include "nsIXPCScriptable.h"
+#include "mozilla/Attributes.h"
 
 namespace mozilla {
 namespace reflect {
 
-class Module : public nsIXPCScriptable
+class Module MOZ_FINAL : public nsIXPCScriptable
 {
 public:
   NS_DECL_ISUPPORTS
diff --git a/toolkit/components/startup/nsAppStartup.h b/toolkit/components/startup/nsAppStartup.h
index 2f4d2c0873d5..200f9834d344 100644
--- a/toolkit/components/startup/nsAppStartup.h
+++ b/toolkit/components/startup/nsAppStartup.h
@@ -13,6 +13,7 @@
 
 #include "nsINativeAppSupport.h"
 #include "nsIAppShell.h"
+#include "mozilla/Attributes.h"
 
 #if defined(XP_WIN)
 //XPerf-backed probes
@@ -28,10 +29,10 @@ struct PLEvent;
 { 0x7dd4d320, 0xc84b, 0x4624, { 0x8d, 0x45, 0x7b, 0xb9, 0xb2, 0x35, 0x69, 0x77 } }
 
 
-class nsAppStartup : public nsIAppStartup,
-                     public nsIWindowCreator2,
-                     public nsIObserver,
-                     public nsSupportsWeakReference
+class nsAppStartup MOZ_FINAL : public nsIAppStartup,
+                               public nsIWindowCreator2,
+                               public nsIObserver,
+                               public nsSupportsWeakReference
 {
 public:
   NS_DECL_ISUPPORTS
diff --git a/toolkit/components/telemetry/Telemetry.cpp b/toolkit/components/telemetry/Telemetry.cpp
index 2ea7a3f04f47..4ebe735184c7 100644
--- a/toolkit/components/telemetry/Telemetry.cpp
+++ b/toolkit/components/telemetry/Telemetry.cpp
@@ -25,6 +25,7 @@
 #include "mozilla/Mutex.h"
 #include "mozilla/FileUtils.h"
 #include "mozilla/Preferences.h"
+#include "mozilla/Attributes.h"
 
 namespace {
 
@@ -85,7 +86,7 @@ AutoHashtable<EntryType>::ReflectIntoJS(ReflectEntryFunc entryFunc,
   return num == this->Count();
 }
 
-class TelemetryImpl : public nsITelemetry
+class TelemetryImpl MOZ_FINAL : public nsITelemetry
 {
   NS_DECL_ISUPPORTS
   NS_DECL_NSITELEMETRY
diff --git a/toolkit/devtools/debugger/nsJSInspector.h b/toolkit/devtools/debugger/nsJSInspector.h
index f0d5e2daab18..cb2265721de8 100644
--- a/toolkit/devtools/debugger/nsJSInspector.h
+++ b/toolkit/devtools/debugger/nsJSInspector.h
@@ -7,11 +7,12 @@
 #define COMPONENTS_JSINSPECTOR_H
 
 #include "nsIJSInspector.h"
+#include "mozilla/Attributes.h"
 
 namespace mozilla {
 namespace jsinspector {
 
-class nsJSInspector : public nsIJSInspector
+class nsJSInspector MOZ_FINAL : public nsIJSInspector
 {
 public:
   NS_DECL_ISUPPORTS
diff --git a/toolkit/system/osxproxy/nsOSXSystemProxySettings.mm b/toolkit/system/osxproxy/nsOSXSystemProxySettings.mm
index 102201828cb4..ef4553f89d3b 100644
--- a/toolkit/system/osxproxy/nsOSXSystemProxySettings.mm
+++ b/toolkit/system/osxproxy/nsOSXSystemProxySettings.mm
@@ -15,8 +15,9 @@
 #include "nsISupportsPrimitives.h"
 #include "nsIURI.h"
 #include "nsObjCExceptions.h"
+#include "mozilla/Attributes.h"
 
-class nsOSXSystemProxySettings : public nsISystemProxySettings {
+class nsOSXSystemProxySettings MOZ_FINAL : public nsISystemProxySettings {
 public:
   NS_DECL_ISUPPORTS
   NS_DECL_NSISYSTEMPROXYSETTINGS