Ben, I don't quite get this one. There are two ways to drag a browser window: 
1) to drag on the tab area, the browser window is resized to 1/4 of the workspace size during dragging, so in this case the size is fixed. 
2) to drag on the non-tab area of the caption area, the browser window will use window transform the same as the app dragging. The window's size will change depending on the finger position. 

Could you more specific on which case we want to do here? Is this the same issue as  Issue 872528 ?

Hey Daisy, sorry, the example in the video is not super clear. Here's a more illustrative photo: https://drive.google.com/file/d/1-0LzsIeLj8hTP4Nf5KGh9BhUiR4dIXXz/view?usp=sharing

The bug is about 1). When there are other fullscreen browser windows in overview as thumbnails, the contrast in size of the top bar between the dragged (and now dropped) tab versus the other windows is quite noticeable. Currently the bounds of the dragged tab window change to fullscreen once it's tapped on. If possible, it would be great if we could change those bounds on drop instead.

Now I get it. Thank you!

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/017cad775d7affe80efb2113bc0c7a00d7114bc6

commit 017cad775d7affe80efb2113bc0c7a00d7114bc6
Author: Xiaoqian Dai <xdai@chromium.org>
Date: Tue Aug 21 18:10:07 2018

Tab dragging: Update the dragged window's bounds before adding to overview.

Before the dragged window is added to overview, its bounds might needs
to update as the dragged window's bounds might have changed during
dragging and as a result its transform might be different with other
window's transform in overview.

Bug:  873284 
Change-Id: I1257f8d4526b62bcf6d3174f611bc4d576818755
Reviewed-on: https://chromium-review.googlesource.com/1180376
Commit-Queue: Xiaoqian Dai <xdai@chromium.org>
Reviewed-by: Mitsuru Oshima (Slow) <oshima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#584821}
[modify] https://crrev.com/017cad775d7affe80efb2113bc0c7a00d7114bc6/ash/wm/overview/window_grid.cc
[modify] https://crrev.com/017cad775d7affe80efb2113bc0c7a00d7114bc6/ash/wm/splitview/split_view_controller_unittest.cc