Add option to force document level passive event listeners as a runtime feature.

third_party/WebKit/Source/core/events/EventTarget.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  *           (C) 2007, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ skipping 181 matching lines @@
             options.setPassive(false);
         return;
     }
 
     if (LocalDOMWindow* executingWindow = this->executingWindow()) {
         if (options.hasPassive()) {
             UseCounter::count(executingWindow->document(), options.passive() ? UseCounter::AddEventListenerPassiveTrue : UseCounter::AddEventListenerPassiveFalse);
         }
     }
 
+    if (RuntimeEnabledFeatures::passiveDocumentEventListenersEnabled()) {
+        if (!options.hasPassive()) {
+            if (Node* node = toNode()) {
+                if (node->isDocumentNode() || node->document().documentElement() == node || node->document().body() == node) {
+                    options.setPassive(true);
+                    return;
+                }
+            } else if (toLocalDOMWindow()) {
+                options.setPassive(true);
+                return;
+            }
+        }
+    }
+
     if (Settings* settings = windowSettings(executingWindow())) {
         switch (settings->passiveListenerDefault()) {
         case PassiveListenerDefault::False:
             if (!options.hasPassive())
                 options.setPassive(false);
             break;
         case PassiveListenerDefault::True:
             if (!options.hasPassive())
                 options.setPassive(true);
             break;
         case PassiveListenerDefault::ForceAllTrue:
             options.setPassive(true);
             break;
-        case PassiveListenerDefault::DocumentTrue:
-            if (!options.hasPassive()) {
-                if (Node* node = toNode()) {
-                    if (node->isDocumentNode() || node->document().documentElement() == node || node->document().body() == node) {
-                        options.setPassive(true);
-                    }
-                } else if (toLocalDOMWindow()) {
-                    options.setPassive(true);
-                }
-            }
-            break;
         }
     } else {
         if (!options.hasPassive())
             options.setPassive(false);
     }
 }
 
 bool EventTarget::addEventListener(const AtomicString& eventType, EventListener* listener, bool useCapture)
 {
     AddEventListenerOptions options;
@@ skipping 412 matching lines @@
     // they have one less listener to invoke.
     if (d->firingEventIterators) {
         for (size_t i = 0; i < d->firingEventIterators->size(); ++i) {
             d->firingEventIterators->at(i).iterator = 0;
             d->firingEventIterators->at(i).end = 0;
         }
     }
 }
 
 } // namespace blink