Delegate dragend to the correct frame's EventHandler.

third_party/WebKit/Source/core/input/EventHandler.cpp

Index: third_party/WebKit/Source/core/input/EventHandler.cpp
diff --git a/third_party/WebKit/Source/core/input/EventHandler.cpp b/third_party/WebKit/Source/core/input/EventHandler.cpp
index a40a5bc065dff8cd721b95a119fcf4bc36e0dad3..cf568d1e27b0cbd584a6060df42f4b5156fc528b 100644
--- a/third_party/WebKit/Source/core/input/EventHandler.cpp
+++ b/third_party/WebKit/Source/core/input/EventHandler.cpp
@@ -1967,7 +1967,15 @@ void EventHandler::defaultKeyboardEventHandler(KeyboardEvent* event) {
 
 void EventHandler::dragSourceEndedAt(const PlatformMouseEvent& event,
                                      DragOperation operation) {
-  m_mouseEventManager->dragSourceEndedAt(event, operation);
+  HitTestRequest request(HitTestRequest::ReadOnly);
+  MouseEventWithHitTestResults mev =
+      EventHandlingUtil::performMouseEventHitTest(m_frame, request, event);
+
+  LocalFrame* targetFrame;
+  if (targetIsFrame(mev.innerNode(), targetFrame))
+    targetFrame->eventHandler().dragSourceEndedAt(event, operation);

[dcheng, 2016/11/03 03:09:59]

Specifically, null-checking targetFrame here fixes both failing test locally for
me.

+  else
+    m_mouseEventManager->dragSourceEndedAt(event, operation);
 }
 
 void EventHandler::updateDragStateAfterEditDragIfNeeded(