i think this request is out of my depth, and requires a bit of discussion first.

there are only three dispositions currently registered everywhere [1]:
  currentTab
  newForegroundTab
  newBackgroundTab

it doesn't sound like reusing any of those is appropriate here.  so we'd need to plumb through "newForegroundWindow" in the JS/C++ code.

i'm guessing you want it to open a new window with one tab by default rather than open a new window with no chrome ?  i.e. you want window.open(chrome=yes) ?

[1] https://developer.chrome.com/extensions/omnibox#type-OnInputEnteredDisposition

vapier: I'm not sure what you mean by the dispositions being registered. You're referring, I guess, to the extensions API?

Regardless, just to make sure I knew what's going on, I tried this real quick and using the NEW_WINDOW disposition and it seemed to work fine. Since I already have a bit of code, I'll go ahead and send out a CL.

i guess WindowOpenDisposition::NEW_WINDOW already exists (so the C++ side is done), and omnibox_api.cc has a fallback for unknown dispositions, so simply updating omnibox_view_views.cc doesn't require JS updates (although it'd be nice).  Shift-Enter will continue to trigger currentTab.

My CL to enable shift-enter has nearly landed. Reducing priority to P3 for tracking the desire to update the JS to match.

i can roll the JS side if you want

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/135777191e6d978d8e54b5f6cbfadcefe3d3aa49

commit 135777191e6d978d8e54b5f6cbfadcefe3d3aa49
Author: Justin Donnelly <jdonnelly@chromium.org>
Date: Mon Jul 16 14:54:27 2018

[omnibox] Add shift-enter handling to the selected suggestion.

Shift-enter will open the currently selected match in a new window. The
primary purpose of this change is to avoid regressing the existing Cocoa
behavior when MacViews launches. However, it seems just as useful on all
desktop platforms and shift-enter isn't currently in use for anything
else.

Also, remove some dead code that was added to support tab switch back in
https://crrev.com/c/809527. We don't use this shift-enter behavior
anymore so the OnShiftKeyChanged method is no longer needed.

Bug: 863156
Change-Id: I41960db2dd3a81be0ba79db90b2e69a69cf50031
Reviewed-on: https://chromium-review.googlesource.com/1136651
Reviewed-by: Kevin Bailey <krb@chromium.org>
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Justin Donnelly <jdonnelly@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575261}
[modify] https://crrev.com/135777191e6d978d8e54b5f6cbfadcefe3d3aa49/chrome/browser/ui/cocoa/omnibox/omnibox_view_mac.mm
[modify] https://crrev.com/135777191e6d978d8e54b5f6cbfadcefe3d3aa49/chrome/browser/ui/views/omnibox/omnibox_view_views.cc
[modify] https://crrev.com/135777191e6d978d8e54b5f6cbfadcefe3d3aa49/components/omnibox/browser/omnibox_view.cc
[modify] https://crrev.com/135777191e6d978d8e54b5f6cbfadcefe3d3aa49/components/omnibox/browser/omnibox_view.h

Assigning to vapier for handling the JS side of this change. Thanks!