Update web classes to use OVERRIDE / FINAL when needed

Source/web/WebHelperPluginImpl.h

Index: Source/web/WebHelperPluginImpl.h
diff --git a/Source/web/WebHelperPluginImpl.h b/Source/web/WebHelperPluginImpl.h
index fde92b483e9b8e35c4a18013805511b7c2ddb97d..f1af4101d8846c2a437fb438ac67983065d1bb12 100644
--- a/Source/web/WebHelperPluginImpl.h
+++ b/Source/web/WebHelperPluginImpl.h
@@ -50,8 +50,7 @@ class WebWidgetClient;
 
 // Hosts a simple page that instantiates a plugin using an <object> tag.
 // The widget is offscreen, and the plugin will not receive painting, resize, etc. events.
-class WebHelperPluginImpl : public WebHelperPlugin,
-                            public RefCounted<WebHelperPluginImpl> {
+class WebHelperPluginImpl FINAL : public WebHelperPlugin, public RefCounted<WebHelperPluginImpl> {
     WTF_MAKE_NONCOPYABLE(WebHelperPluginImpl);
     WTF_MAKE_FAST_ALLOCATED;