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

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

Index: third_party/WebKit/Source/core/events/EventTarget.cpp
diff --git a/third_party/WebKit/Source/core/events/EventTarget.cpp b/third_party/WebKit/Source/core/events/EventTarget.cpp
index 0e63681afa13968b740bfcbab3032796d84d8acf..92bd274edfce15a084ab1bacf2935052978e3aef 100644
--- a/third_party/WebKit/Source/core/events/EventTarget.cpp
+++ b/third_party/WebKit/Source/core/events/EventTarget.cpp
@@ -199,6 +199,20 @@ void EventTarget::setDefaultAddEventListenerOptions(const AtomicString& eventTyp
         }
     }
 
+    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:
@@ -212,17 +226,6 @@ void EventTarget::setDefaultAddEventListenerOptions(const AtomicString& eventTyp
         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())