Add UMA metrics for root scroller intervention to track forcing passive breakage.

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

Index: third_party/WebKit/Source/core/events/Event.cpp
diff --git a/third_party/WebKit/Source/core/events/Event.cpp b/third_party/WebKit/Source/core/events/Event.cpp
index 1c5361af5ce8fb380044a3bea8b94d1643824e3f..75354650ffca4cc03ee2ca562fd5c8d137d1b14a 100644
--- a/third_party/WebKit/Source/core/events/Event.cpp
+++ b/third_party/WebKit/Source/core/events/Event.cpp
@@ -225,6 +225,7 @@ bool Event::isBeforeUnloadEvent() const
 void Event::preventDefault()
 {
     if (m_handlingPassive) {
+        m_preventDefaultCalledDuringPassive = true;
         const LocalDOMWindow* window = m_eventPath ? m_eventPath->windowEventContext().window() : 0;
         if (window)
             window->printErrorMessage("Unable to preventDefault inside passive event listener invocation.");
@@ -277,6 +278,12 @@ HeapVector<Member<EventTarget>> Event::composedPath(ScriptState* scriptState) co
     return pathInternal(scriptState, EmptyAfterDispatch);
 }
 
+void Event::setHandlingPassive(bool value)
+{
+    m_handlingPassive = value;
+    m_preventDefaultCalledDuringPassive = false;
+}
+
 HeapVector<Member<EventTarget>> Event::pathInternal(ScriptState* scriptState, EventPathMode mode) const
 {
     if (m_target)