Add Event.isTrusted support

Source/core/events/Event.cpp

Index: Source/core/events/Event.cpp
diff --git a/Source/core/events/Event.cpp b/Source/core/events/Event.cpp
index 397206955ee51cc1b58b90afd82fecdd231726e3..c49e49e9f9641b5f33381901bf08b78aa697177b 100644
--- a/Source/core/events/Event.cpp
+++ b/Source/core/events/Event.cpp
@@ -47,6 +47,7 @@ Event::Event(const AtomicString& eventType, bool canBubbleArg, bool cancelableAr
     , m_defaultPrevented(false)
     , m_defaultHandled(false)
     , m_cancelBubble(false)
+    , m_isTrusted(false)
     , m_eventPhase(0)
     , m_currentTarget(nullptr)
     , m_createTime(convertSecondsToDOMTimeStamp(currentTime()))
@@ -71,6 +72,7 @@ void Event::initEvent(const AtomicString& eventTypeArg, bool canBubbleArg, bool
     m_propagationStopped = false;
     m_immediatePropagationStopped = false;
     m_defaultPrevented = false;
+    m_isTrusted = false;
 
     m_type = eventTypeArg;
     m_canBubble = canBubbleArg;