The 'system_info' is only used in status monitor plugin, so it is possibly to make following changes:

1. Remove 'system_info' from state
2. Remove 'UPDATE_SYSTEM_INFO' and 'SYSTEM_INFO' events (from test/event.py)
3. Fetch system_info via a new RPC function from status monitor plugin

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform/factory/+/ce8ffe05c82350caf97aa0aed69bf5a9a808c8d7

commit ce8ffe05c82350caf97aa0aed69bf5a9a808c8d7
Author: Shen-En Shih <petershih@chromium.org>
Date: Mon Aug 07 07:19:20 2017

goofy: Remove 'system_info' from state

The 'system_info' is now removed from state. One of the
related events is 'SYSTEM_INFO', which is designed to
get the updated device info. Now, to read the device info,
one should use the `device.info` to fetch properties.

Another related event is 'UPDATE_SYSTEM_INFO'. This event
can still be used to notify the change of one or more device
properties. So each event client can update its component
correctly (e.g., the status monitor plugin).

BUG= chromium:751026 
TEST=make test

Change-Id: I4a0cfe007c3e2fce54694b6b71bd8dd8be50f56d
Reviewed-on: https://chromium-review.googlesource.com/595791
Commit-Ready: Shen-En Shih <petershih@chromium.org>
Tested-by: Shen-En Shih <petershih@chromium.org>
Reviewed-by: Hung-Te Lin <hungte@chromium.org>

[modify] https://crrev.com/ce8ffe05c82350caf97aa0aed69bf5a9a808c8d7/py/test/event.py
[modify] https://crrev.com/ce8ffe05c82350caf97aa0aed69bf5a9a808c8d7/py/goofy/goofy.py

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform/factory/+/fab2c2ce423ff01652c132f79fd22620e4c0f20d

commit fab2c2ce423ff01652c132f79fd22620e4c0f20d
Author: Shen-En Shih <petershih@chromium.org>
Date: Mon Aug 07 07:19:21 2017

status-monitor: Fetch device info from `device.info`

When the device info is changed, the 'UpdateDevieInfo' RPC
call will be called. The status monitor plugin should
update the device info on UI after received this call.

To support this, I choose to modify the 'GetSystemStatus'
RPC call. Originally, this call only returns the dynamic
system status like CPU loading and battery info. Now,
it also returns the updated device info, if the device info
is needed to be updated.

To reflect this change, the name of this RPC call is also
changed from 'GetSystemStatus' to 'GetSystemInfo'.

BUG= chromium:751026 
TEST=make test

Change-Id: I4091a9482fc0e99abbf5459283ac26ea5c958ac0
Reviewed-on: https://chromium-review.googlesource.com/595790
Commit-Ready: Shen-En Shih <petershih@chromium.org>
Tested-by: Shen-En Shih <petershih@chromium.org>
Reviewed-by: Hung-Te Lin <hungte@chromium.org>

[modify] https://crrev.com/fab2c2ce423ff01652c132f79fd22620e4c0f20d/py/goofy/plugins/status_monitor/static/status_monitor.js
[modify] https://crrev.com/fab2c2ce423ff01652c132f79fd22620e4c0f20d/py/goofy/plugins/status_monitor/status_monitor.py