Aseda tells me the tablet mode switch only asserts at ~300 degrees, which matches what we see here. In normal tablet mode (without external display), the device switches from clamshell to touchview UI as soon as it passes 180 degrees. But in docked mode, the UI stays in clamshell (with keyboard usable) after 180 degrees until you bend it to about 300 degrees, when it suddenly switches into touchview anyway.

So it seems like Chrome normally decides to switch to touchview based on accelerometer data once it passes 180, and that code correctly knows about the docked mode exception. But then there seems to be another part that always forces touchview when the EC tablet mode flag is asserted, and that one ignores docked mode. That part needs to be fixed.

One other thing that I forgot to mention is that the state seems to be stuck until you disconnect the external display. Using ectool, I can confirm that the kernel is receiving the new accelerometer readings, but the external display is still in touchview until either the lid is closed or the external display is disconnected.

The ability to use the keyboard with the internal display off was added to accelerometer based checks: https://cs.chromium.org/chromium/src/ash/common/wm/maximize_mode/maximize_mode_controller.cc?rcl=1484943409&l=191

However this is not checked when receiving the tablet mode switch:
https://cs.chromium.org/chromium/src/ash/common/wm/maximize_mode/maximize_mode_controller.cc?rcl=1484943409&l=225

I'm pretty sure that all we need to do is replicate the no internal display check in tablet mode switch code. However I lack the hardware to verify this.

https://codereview.chromium.org/2649553004/

> I'm pretty sure that all we need to do is replicate the no internal display check in tablet mode switch code. However I lack the hardware to verify this.

Aseda is out sick and I don't really have the full setup needed to recompile Chrome. :/

I think what needs to be done in the code is very straight-forward, like you said. If you could just check it in, I can test it for you as soon as the first canary image comes out.

I spoke with gwendal, and there was a missed case in the original patch.

I'll add tests this afternoon and pursue landing.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/1d03b9255a7b9ccdb4047d57e78e70e6cf1db0b8

commit 1d03b9255a7b9ccdb4047d57e78e70e6cf1db0b8
Author: jonross <jonross@chromium.org>
Date: Thu Jan 26 01:37:53 2017

Do not enter Maximize Mode while docked

Update the handling of the tablet mode switch to not trigger maximize mode if
the device is currently docked.

BUG= 682859 

Review-Url: https://codereview.chromium.org/2649553004
Cr-Commit-Position: refs/heads/master@{#446195}

[modify] https://crrev.com/1d03b9255a7b9ccdb4047d57e78e70e6cf1db0b8/ash/common/wm/maximize_mode/maximize_mode_controller.cc
[modify] https://crrev.com/1d03b9255a7b9ccdb4047d57e78e70e6cf1db0b8/ash/wm/maximize_mode/maximize_mode_controller_unittest.cc

Verified on kevin and elm on R58-9235.0.0.