https://codereview.chromium.org/2962923003/ has a simple implementation.

Screenshot 1 is of the single item drag.

Screenshots 2 and 3 are 2 options for the multi-item drag. 3 is based on drive's multi-item drag and is the one we're proceeding with.

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The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/de8088188edebdcfbc05eb14cd5a238c25ae2fc2

commit de8088188edebdcfbc05eb14cd5a238c25ae2fc2
Author: calamity <calamity@chromium.org>
Date: Tue Jul 04 09:53:08 2017

[MD Bookmarks] Add drag and drop indicator.

This CL adds a drag and drop chip which displays the item icon and title
when dragging.

BUG= 729860 
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2962923003
Cr-Commit-Position: refs/heads/master@{#484079}

[modify] https://crrev.com/de8088188edebdcfbc05eb14cd5a238c25ae2fc2/chrome/browser/browser_resources.grd
[modify] https://crrev.com/de8088188edebdcfbc05eb14cd5a238c25ae2fc2/chrome/browser/resources/md_bookmarks/bookmarks.html
[modify] https://crrev.com/de8088188edebdcfbc05eb14cd5a238c25ae2fc2/chrome/browser/resources/md_bookmarks/compiled_resources2.gyp
[add] https://crrev.com/de8088188edebdcfbc05eb14cd5a238c25ae2fc2/chrome/browser/resources/md_bookmarks/dnd_chip.html
[add] https://crrev.com/de8088188edebdcfbc05eb14cd5a238c25ae2fc2/chrome/browser/resources/md_bookmarks/dnd_chip.js
[modify] https://crrev.com/de8088188edebdcfbc05eb14cd5a238c25ae2fc2/chrome/browser/resources/md_bookmarks/dnd_manager.html
[modify] https://crrev.com/de8088188edebdcfbc05eb14cd5a238c25ae2fc2/chrome/browser/resources/md_bookmarks/dnd_manager.js
[modify] https://crrev.com/de8088188edebdcfbc05eb14cd5a238c25ae2fc2/chrome/browser/ui/webui/md_bookmarks/md_bookmarks_ui.cc
[modify] https://crrev.com/de8088188edebdcfbc05eb14cd5a238c25ae2fc2/chrome/test/data/webui/md_bookmarks/dnd_manager_test.js

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/571711199808b424ff2d60d9295ef6d802e31c87

commit 571711199808b424ff2d60d9295ef6d802e31c87
Author: calamity <calamity@chromium.org>
Date: Thu Jul 06 06:33:06 2017

[MD Bookmarks] Add UI for multi-item drag and drop chip.

This CL makes a secondary div appear behind the drag and drop chip and
a count that shows the number of items being dragged when more than 1
item is dragged.

BUG= 729860 
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2972633002
Cr-Commit-Position: refs/heads/master@{#484479}

[modify] https://crrev.com/571711199808b424ff2d60d9295ef6d802e31c87/chrome/browser/resources/md_bookmarks/dnd_chip.html
[modify] https://crrev.com/571711199808b424ff2d60d9295ef6d802e31c87/chrome/browser/resources/md_bookmarks/dnd_chip.js
[modify] https://crrev.com/571711199808b424ff2d60d9295ef6d802e31c87/chrome/browser/resources/md_bookmarks/dnd_manager.js
[modify] https://crrev.com/571711199808b424ff2d60d9295ef6d802e31c87/chrome/browser/resources/md_bookmarks/shared_style.html

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3719676a54b6d982171bd2faac4c4b84135b1e69

commit 3719676a54b6d982171bd2faac4c4b84135b1e69
Author: Christopher Lam <calamity@chromium.org>
Date: Tue Jul 25 03:43:17 2017

[MD Bookmarks] Update drag and drop chip style.

Bug:  729860 
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I28780aacdfc5e11c27ab25e413e4db46765b705e
Reviewed-on: https://chromium-review.googlesource.com/580052
Commit-Queue: calamity <calamity@chromium.org>
Reviewed-by: Tim Sergeant <tsergeant@chromium.org>
Cr-Commit-Position: refs/heads/master@{#489217}
[modify] https://crrev.com/3719676a54b6d982171bd2faac4c4b84135b1e69/chrome/browser/resources/md_bookmarks/dnd_chip.html