Delegate dragend to the correct frame's EventHandler.

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

Index: third_party/WebKit/Source/core/input/MouseEventManager.cpp
diff --git a/third_party/WebKit/Source/core/input/MouseEventManager.cpp b/third_party/WebKit/Source/core/input/MouseEventManager.cpp
index 34e32b79981294c4542d26317a7d407db563a378..c6ca97f15fcfe49cd2e9639e71aaab779b0763f7 100644
--- a/third_party/WebKit/Source/core/input/MouseEventManager.cpp
+++ b/third_party/WebKit/Source/core/input/MouseEventManager.cpp
@@ -908,7 +908,10 @@ void MouseEventManager::clearDragDataTransfer() {
 void MouseEventManager::dragSourceEndedAt(const PlatformMouseEvent& event,
                                           DragOperation operation) {
   // Send a hit test request so that Layer gets a chance to update the :hover
-  // and :active pseudoclasses..
+  // and :active pseudoclasses.
+  // TODO(crbug.com/661842): This should be redundant with the hit test in
+  // EventHandler::dragSourceEndedAt, but isn't. Figure out why, then remove the
+  // test here.
   HitTestRequest request(HitTestRequest::Release);
   EventHandlingUtil::performMouseEventHitTest(m_frame, request, event);