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

third_party/WebKit/Source/web/WebRuntimeFeatures.cpp

Index: third_party/WebKit/Source/web/WebRuntimeFeatures.cpp
diff --git a/third_party/WebKit/Source/web/WebRuntimeFeatures.cpp b/third_party/WebKit/Source/web/WebRuntimeFeatures.cpp
index e68345d9246e54a2423e6c6e9d47cf327b5ca4c1..0e707c4bd218be276979b01026dbd2f610ff0fe2 100644
--- a/third_party/WebKit/Source/web/WebRuntimeFeatures.cpp
+++ b/third_party/WebKit/Source/web/WebRuntimeFeatures.cpp
@@ -200,6 +200,11 @@ void WebRuntimeFeatures::enableParseHTMLOnMainThread(bool enable)
     RuntimeEnabledFeatures::setParseHTMLOnMainThreadEnabled(enable);
 }
 
+void WebRuntimeFeatures::enablePassiveDocumentEventListeners(bool enable)
+{
+    RuntimeEnabledFeatures::setPassiveDocumentEventListenersEnabled(enable);
+}
+
 void WebRuntimeFeatures::enablePermissionsAPI(bool enable)
 {
     RuntimeEnabledFeatures::setPermissionsEnabled(enable);