Oilpan: Replace EAGERLY_FINALIZE in EventTarget's hierarchy with pre-finalizers

third_party/WebKit/Source/modules/mediastream/RTCDTMFSender.cpp

Index: third_party/WebKit/Source/modules/mediastream/RTCDTMFSender.cpp
diff --git a/third_party/WebKit/Source/modules/mediastream/RTCDTMFSender.cpp b/third_party/WebKit/Source/modules/mediastream/RTCDTMFSender.cpp
index 1e591a6d2d2c249b5814c45f2ffb2569490e1056..89c3433f271751fc19add5af55bfedd275545f74 100644
--- a/third_party/WebKit/Source/modules/mediastream/RTCDTMFSender.cpp
+++ b/third_party/WebKit/Source/modules/mediastream/RTCDTMFSender.cpp
@@ -65,6 +65,7 @@ RTCDTMFSender::RTCDTMFSender(ExecutionContext* context, MediaStreamTrack* track,
     , m_stopped(false)
     , m_scheduledEventTimer(this, &RTCDTMFSender::scheduledEventTimerFired)
 {
+    ThreadState::current()->registerPreFinalizer(this);
     m_handler->setClient(this);
 }
 
@@ -72,6 +73,14 @@ RTCDTMFSender::~RTCDTMFSender()
 {
 }
 
+void RTCDTMFSender::dispose()
+{
+    // Promptly clears a raw reference from content/ to an on-heap object
+    // so that content/ doesn't access it in a lazy sweeping phase.
+    m_handler->setClient(nullptr);
+    m_handler.clear();
+}
+
 bool RTCDTMFSender::canInsertDTMF() const
 {
     return m_handler->canInsertDTMF();
@@ -139,7 +148,7 @@ ExecutionContext* RTCDTMFSender::getExecutionContext() const
 void RTCDTMFSender::stop()
 {
     m_stopped = true;
-    m_handler->setClient(0);
+    m_handler->setClient(nullptr);
 }
 
 void RTCDTMFSender::scheduleDispatchEvent(Event* event)