So different size for the preview when it's a photo compared to when it's an avatar image?

It's fine to have different size for the preview when it's a photo compared to when it's an avatar image.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e6f8a17f8a836cc31b558e0894f6f18ae98254df

commit e6f8a17f8a836cc31b558e0894f6f18ae98254df
Author: David Reveman <reveman@chromium.org>
Date: Thu Aug 24 20:22:37 2017

WebUI: Display photo preview at 288px size.

This makes the photo preview the same size as the camera, 288px.
Normal preview (without a discard button) will still be at 192px
and centered.

This will also adjust the capture size to ensure that photo taken
is still crisp on hi-dpi devices.

Bug:  758086 
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: Ibd15680cf03e5416f9069496041061121dc643c4
Reviewed-on: https://chromium-review.googlesource.com/631096
Commit-Queue: David Reveman <reveman@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#497175}
[modify] https://crrev.com/e6f8a17f8a836cc31b558e0894f6f18ae98254df/ui/webui/resources/cr_elements/chromeos/cr_picture/cr_camera.js
[modify] https://crrev.com/e6f8a17f8a836cc31b558e0894f6f18ae98254df/ui/webui/resources/cr_elements/chromeos/cr_picture/cr_picture_pane.html

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/73cb5d0606100491bd15dd55b5d92401ee81b7f9

commit 73cb5d0606100491bd15dd55b5d92401ee81b7f9
Author: David Reveman <reveman@chromium.org>
Date: Fri Aug 25 08:19:33 2017

WebUI: Display photo preview at 288px size.

This makes the photo preview the same size as the camera, 288px.
Normal preview (without a discard button) will still be at 192px
and centered.

This will also adjust the capture size to ensure that photo taken
is still crisp on hi-dpi devices.

TBR=reveman@chromium.org

(cherry picked from commit e6f8a17f8a836cc31b558e0894f6f18ae98254df)

Bug:  758086 
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: Ibd15680cf03e5416f9069496041061121dc643c4
Reviewed-on: https://chromium-review.googlesource.com/631096
Commit-Queue: David Reveman <reveman@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#497175}
Reviewed-on: https://chromium-review.googlesource.com/634987
Reviewed-by: David Reveman <reveman@chromium.org>
Cr-Commit-Position: refs/branch-heads/3163@{#885}
Cr-Branched-From: ff259bab28b35d242e10186cd63af7ed404fae0d-refs/heads/master@{#488528}
[modify] https://crrev.com/73cb5d0606100491bd15dd55b5d92401ee81b7f9/ui/webui/resources/cr_elements/chromeos/cr_picture/cr_camera.js
[modify] https://crrev.com/73cb5d0606100491bd15dd55b5d92401ee81b7f9/ui/webui/resources/cr_elements/chromeos/cr_picture/cr_picture_pane.html