Check detached status before attempting to clear drag transfer state (reland.)

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 8d2c670cd796112fce75c2bf9b56adadc99b660b..802b434398571b4a76d8cc64f8df4e9c83421b66 100644
--- a/third_party/WebKit/Source/core/input/MouseEventManager.cpp
+++ b/third_party/WebKit/Source/core/input/MouseEventManager.cpp
@@ -945,6 +945,8 @@ WebInputEventResult MouseEventManager::dispatchDragEvent(
 }
 
 void MouseEventManager::clearDragDataTransfer() {
+  if (!m_frame->page())
+    return;
   if (dragState().m_dragDataTransfer) {
     dragState().m_dragDataTransfer->clearDragImage();
     dragState().m_dragDataTransfer->setAccessPolicy(DataTransferNumb);