Chrome Version       : 51.0.2700.0
OS Version: OS X 10.11.4

This is basically the Mac version of  Issue 336691  for views. Views added code to handle the case and prevent it, but it's sadly not automatically hooked up for MacViews (we need a delegate, which is currently NOTIMPLEMENTED).

On Mac (both Views and Cocoa) it "copes", but it's a bit weird.


What steps will reproduce the problem?
1. Have 2 windows (give them different content to see the next steps)
2. Press Cmd+s in one window to get a modal sheet
3. Drag the tab in the other window onto the window with the modal sheet.

What is the expected result?

Dragging should be prevented (that's what happens on Views anyway).

Alternatives: maybe it should attach as a background tab? Or maybe the modal save dialog should get automatically dismissed?


What happens instead of that?

Tab gets attached as a foreground tab. Window modal save dialog is still shown, but it's now on top of the "wrong" tab -- the one just dragged in rather than the tab it was opened for. Committing the Save saves the original tab (not the one dragged in).