1 files changed, 10 insertions, 0 deletions
diff --git a/src/core/web_contents_adapter.cpp b/src/core/web_contents_adapter.cpp
index 7285648fd..fc54c98ed 100644
--- a/src/core/web_contents_adapter.cpp
+++ b/src/core/web_contents_adapter.cpp
@@ -1159,6 +1159,16 @@ Qt::DropAction WebContentsAdapter::updateDragPosition(QDragMoveEvent *e, const Q
     rvh->DragTargetDragOver(toGfx(e->pos()), toGfx(screenPos), toWeb(e->possibleActions()),
                             blink::WebInputEvent::LeftButtonDown);
 
+    base::MessageLoop *currentMessageLoop = base::MessageLoop::current();
+    DCHECK(currentMessageLoop);
+    if (!currentMessageLoop->NestableTasksAllowed()) {
+        // We're already inside a MessageLoop::RunTask call, and scheduled tasks will not be
+        // executed. That means, updateDragAction will never be called, and the RunLoop below will
+        // remain blocked forever.
+        qWarning("WebContentsAdapter::updateDragPosition called from MessageLoop::RunTask.");
+        return Qt::IgnoreAction;
+    }
+
     // Wait until we get notified via RenderViewHostDelegateView::UpdateDragCursor. This calls
     // WebContentsAdapter::updateDragAction that will eventually quit the nested loop.
     base::RunLoop loop;