I can't recall 100% if we just arbitrarily chose the lower angle number, or if this was influenced by panel viewing angles on the original convertibles.

However that predates Android, and how software is interacting with the api. So I'm fine with changing this.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/162e929b0c95fb19191e907efbcb9feeadcfe642

commit 162e929b0c95fb19191e907efbcb9feeadcfe642
Author: Mitsuru Oshima <oshima@chromium.org>
Date: Tue Jan 23 16:56:27 2018

Change the default portrait on landscape device to 270

To keep this consistent with Android.

A minor simplification and eliminatd LockRotationToXxxOrientation.

BUG= 802349 
TEST=covered by unit tests. tested manually on landscape and portrait device.

Change-Id: Ide31343f63f637d6057da82e87a11081d330f741
Reviewed-on: https://chromium-review.googlesource.com/877441
Commit-Queue: Mitsuru Oshima <oshima@chromium.org>
Reviewed-by: Jonathan Ross <jonross@chromium.org>
Cr-Commit-Position: refs/heads/master@{#531261}
[modify] https://crrev.com/162e929b0c95fb19191e907efbcb9feeadcfe642/ash/content/display/screen_orientation_controller_chromeos_unittest.cc
[modify] https://crrev.com/162e929b0c95fb19191e907efbcb9feeadcfe642/ash/display/display_manager_unittest.cc
[modify] https://crrev.com/162e929b0c95fb19191e907efbcb9feeadcfe642/ash/display/screen_orientation_controller_chromeos.cc
[modify] https://crrev.com/162e929b0c95fb19191e907efbcb9feeadcfe642/ash/display/screen_orientation_controller_chromeos.h
[modify] https://crrev.com/162e929b0c95fb19191e907efbcb9feeadcfe642/ash/wm/overview/window_selector_unittest.cc
[modify] https://crrev.com/162e929b0c95fb19191e907efbcb9feeadcfe642/ash/wm/splitview/split_view_controller_unittest.cc
[modify] https://crrev.com/162e929b0c95fb19191e907efbcb9feeadcfe642/chrome/browser/ui/ash/launcher/arc_app_window_launcher_controller.cc
[modify] https://crrev.com/162e929b0c95fb19191e907efbcb9feeadcfe642/chrome/browser/ui/ash/launcher/chrome_launcher_controller_unittest.cc