Allow OOPIFs to capture mouse input while mouse button is held down

content/browser/renderer_host/render_widget_host_input_event_router.h

Index: content/browser/renderer_host/render_widget_host_input_event_router.h
diff --git a/content/browser/renderer_host/render_widget_host_input_event_router.h b/content/browser/renderer_host/render_widget_host_input_event_router.h
index ba064ccb1518135248c3901ac5844a5e56809b05..29aa660242cc7c13f11bcee74d30b7752dd46844 100644
--- a/content/browser/renderer_host/render_widget_host_input_event_router.h
+++ b/content/browser/renderer_host/render_widget_host_input_event_router.h
@@ -145,6 +145,8 @@ class CONTENT_EXPORT RenderWidgetHostInputEventRouter
   TargetData touchpad_gesture_target_;
   TargetData bubbling_gesture_scroll_target_;
   TargetData first_bubbling_scroll_target_;
+  // Maintains the same target between mouse down and mouse up.
+  TargetData mouse_capture_target_;
 
   // Tracked for the purpose of generating MouseEnter and MouseLeave events.
   RenderWidgetHostViewBase* last_mouse_move_target_;