Oilpan: trace Event.currentTarget.

Strongly keep track of the current target.

For tidiness, also trace the 'parent' back reference on the XHR progress
event throttling part object.

R=zerny@chromium.org,ager@chromium.org
BUG=340522

Review URL: https://codereview.chromium.org/330273002

git-svn-id: svn://svn.chromium.org/blink/trunk@176112 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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

@@ -47,7 +47,7 @@ Event::Event()
     , m_defaultHandled(false)
     , m_cancelBubble(false)
     , m_eventPhase(0)
-    , m_currentTarget(0)
+    , m_currentTarget(nullptr)
     , m_createTime(convertSecondsToDOMTimeStamp(currentTime()))
 {
     ScriptWrappable::init(this);
@@ -63,7 +63,7 @@ Event::Event(const AtomicString& eventType, bool canBubbleArg, bool cancelableAr
     , m_defaultHandled(false)
     , m_cancelBubble(false)
     , m_eventPhase(0)
-    , m_currentTarget(0)
+    , m_currentTarget(nullptr)
     , m_createTime(convertSecondsToDOMTimeStamp(currentTime()))
 {
     ScriptWrappable::init(this);
@@ -79,7 +79,7 @@ Event::Event(const AtomicString& eventType, const EventInit& initializer)
     , m_defaultHandled(false)
     , m_cancelBubble(false)
     , m_eventPhase(0)
-    , m_currentTarget(0)
+    , m_currentTarget(nullptr)
     , m_createTime(convertSecondsToDOMTimeStamp(currentTime()))
 {
     ScriptWrappable::init(this);
@@ -248,6 +248,7 @@ EventTarget* Event::currentTarget() const
 
 void Event::trace(Visitor* visitor)
 {
+    visitor->trace(m_currentTarget);
     visitor->trace(m_target);
     visitor->trace(m_underlyingEvent);
     visitor->trace(m_eventPath);

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

@@ -203,7 +203,7 @@ private:
     bool m_cancelBubble;
 
     unsigned short m_eventPhase;
-    EventTarget* m_currentTarget;
+    RawPtrWillBeMember<EventTarget> m_currentTarget;
     RefPtrWillBeMember<EventTarget> m_target;
     DOMTimeStamp m_createTime;
     RefPtrWillBeMember<Event> m_underlyingEvent;

third_party/WebKit/Source/core/xml/XMLHttpRequestProgressEventThrottle.cpp

@@ -217,6 +217,7 @@ void XMLHttpRequestProgressEventThrottle::resume()
 
 void XMLHttpRequestProgressEventThrottle::trace(Visitor* visitor)
 {
+    visitor->trace(m_target);
     visitor->trace(m_deferredProgressEvent);
     visitor->trace(m_deferredEvents);
 }

third_party/WebKit/Source/core/xml/XMLHttpRequestProgressEventThrottle.h

@@ -81,8 +81,11 @@ private:
 
     bool hasEventToDispatch() const;
 
-    // Weak pointer to our XMLHttpRequest object as it is the one holding us.
-    EventTarget* m_target;
+    // Non-Oilpan, keep a weak pointer to our XMLHttpRequest object as it is
+    // the one holding us. With Oilpan, a simple strong Member can be used -
+    // this XMLHttpRequestProgressEventThrottle (part) object dies together
+    // with the XMLHttpRequest object.
+    RawPtrWillBeMember<EventTarget> m_target;
 
     bool m_lengthComputable;
     unsigned long long m_loaded;