Oops, thought I was testing the new UI with RemoteMacViews but I was launching from chrome://apps.
Launching from the Applications directory it seems to fail launching entirely.

Double clicking the application it appears to immediately crash.

[10:44:29]~/Applications/Chromium Apps.localized
$ ./Default\ befgnjgfahhfhfdidmfboaofhelikpfb.app/Contents/MacOS/app_mode_loader 
dyld: Library not loaded: @rpath/libbase.dylib
  Referenced from: /Users/alancutter/Applications/Chromium Apps.localized/./Default befgnjgfahhfhfdidmfboaofhelikpfb.app/Contents/MacOS/app_mode_loader
  Reason: image not found
Abort trap: 6

[10:44:44]~/Applications/Chromium Apps.localized
$ Open Default\ befgnjgfahhfhfdidmfboaofhelikpfb.app/
LSOpenURLsWithRole() failed with error -10810 for the file /Users/alancutter/Applications/Chromium Apps.localized/Default befgnjgfahhfhfdidmfboaofhelikpfb.app.

Looks like I just needed to "export DYLD_LIBRARY_PATH=/Users/alancutter/repos/chromium/src/out/release/" to get it to work.

I see a small challenge in that screenshot. The height of the titlebar is set in Chrome via overriding _titlebarHeight in browser_native_widget_window_mac.mm, this would need to get plumbed through to the remote process as well.

https://chromium-review.googlesource.com/c/chromium/src/+/1295251 should do it ...

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/58d6e37818b57d00097c1334efff093ab6d53e3d

commit 58d6e37818b57d00097c1334efff093ab6d53e3d
Author: Christopher Cameron <ccameron@chromium.org>
Date: Tue Oct 23 21:38:24 2018

RemoteMacViews: Populate CreateWindowParams in overrideable method

This fixes the bug where we see two titlebars for PWA windows, and
fixes a longstanding TODO to add needed parameters to the
CreateWindowParams structure.

Update the mojo struct CreateWindowParams to include parameters used
by the various NativeWidgetMac::CreateNSWindow overrides. Include in
these parameters a WindowClass parameter to indicate the subclass of
NativeWidgetMacNSWindow to use.

Add the overrideable method NativeWidgetMac::PopulateCreateWindowParams
to populate the CreateWindowParams structure.

Add plumbing in BrowserWindowFrame to call back into the browser process
to get the overridden titlebar height. Add similar plumbing to
BrowserNativeWidgetWindow to implement _handleFocusToolbarHotKey. With
this in place, BrowserWindowFrame et al no longer have any dependencies
on browser-process classes.

Move BrowserWindowFrame and NativeWidgetMacFramelessNSWindow from
//chrome/browser/ui/views/ over to //ui/views_bridge_mac.

Bug:  897866 
Change-Id: I04d9dd57d2bb98f98899349f2810198103e286b8
Reviewed-on: https://chromium-review.googlesource.com/c/1295251
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Reviewed-by: ccameron <ccameron@chromium.org>
Commit-Queue: ccameron <ccameron@chromium.org>
Cr-Commit-Position: refs/heads/master@{#602109}
[modify] https://crrev.com/58d6e37818b57d00097c1334efff093ab6d53e3d/chrome/browser/ui/BUILD.gn
[modify] https://crrev.com/58d6e37818b57d00097c1334efff093ab6d53e3d/chrome/browser/ui/views/apps/app_window_native_widget_mac.h
[modify] https://crrev.com/58d6e37818b57d00097c1334efff093ab6d53e3d/chrome/browser/ui/views/apps/app_window_native_widget_mac.mm
[modify] https://crrev.com/58d6e37818b57d00097c1334efff093ab6d53e3d/chrome/browser/ui/views/frame/browser_frame_mac.h
[modify] https://crrev.com/58d6e37818b57d00097c1334efff093ab6d53e3d/chrome/browser/ui/views/frame/browser_frame_mac.mm
[modify] https://crrev.com/58d6e37818b57d00097c1334efff093ab6d53e3d/ui/views/BUILD.gn
[modify] https://crrev.com/58d6e37818b57d00097c1334efff093ab6d53e3d/ui/views/cocoa/bridged_native_widget_host_impl.h
[modify] https://crrev.com/58d6e37818b57d00097c1334efff093ab6d53e3d/ui/views/cocoa/bridged_native_widget_host_impl.mm
[modify] https://crrev.com/58d6e37818b57d00097c1334efff093ab6d53e3d/ui/views/widget/native_widget_mac.h
[modify] https://crrev.com/58d6e37818b57d00097c1334efff093ab6d53e3d/ui/views/widget/native_widget_mac.mm
[modify] https://crrev.com/58d6e37818b57d00097c1334efff093ab6d53e3d/ui/views/widget/native_widget_mac_unittest.mm
[modify] https://crrev.com/58d6e37818b57d00097c1334efff093ab6d53e3d/ui/views_bridge_mac/bridged_native_widget_impl.h
[modify] https://crrev.com/58d6e37818b57d00097c1334efff093ab6d53e3d/ui/views_bridge_mac/bridged_native_widget_impl.mm
[rename] https://crrev.com/58d6e37818b57d00097c1334efff093ab6d53e3d/ui/views_bridge_mac/browser_native_widget_window_mac.h
[rename] https://crrev.com/58d6e37818b57d00097c1334efff093ab6d53e3d/ui/views_bridge_mac/browser_native_widget_window_mac.mm
[modify] https://crrev.com/58d6e37818b57d00097c1334efff093ab6d53e3d/ui/views_bridge_mac/mojo/bridged_native_widget.mojom
[modify] https://crrev.com/58d6e37818b57d00097c1334efff093ab6d53e3d/ui/views_bridge_mac/mojo/bridged_native_widget_host.mojom
[rename] https://crrev.com/58d6e37818b57d00097c1334efff093ab6d53e3d/ui/views_bridge_mac/native_widget_mac_frameless_nswindow.h
[rename] https://crrev.com/58d6e37818b57d00097c1334efff093ab6d53e3d/ui/views_bridge_mac/native_widget_mac_frameless_nswindow.mm