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

third_party/WebKit/Source/modules/webusb/USB.cpp

Index: third_party/WebKit/Source/modules/webusb/USB.cpp
diff --git a/third_party/WebKit/Source/modules/webusb/USB.cpp b/third_party/WebKit/Source/modules/webusb/USB.cpp
index 7863b6f80015211fce5af8b6bf679cdcfadfd065..0254cf738ff978339b48df912a4792c7a6156436 100644
--- a/third_party/WebKit/Source/modules/webusb/USB.cpp
+++ b/third_party/WebKit/Source/modules/webusb/USB.cpp
@@ -78,14 +78,22 @@ USB::USB(LocalFrame& frame)
     : ContextLifecycleObserver(frame.document())
     , m_client(USBController::from(frame).client())
 {
+    ThreadState::current()->registerPreFinalizer(this);
     if (m_client)
         m_client->addObserver(this);
 }
 
 USB::~USB()
 {
+}
+
+void USB::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.
     if (m_client)
         m_client->removeObserver(this);
+    m_client = nullptr;
 }
 
 ScriptPromise USB::getDevices(ScriptState* scriptState)