Oops, I forgot to set this bug # when submitting the implementing CLs. Here they are:


(1) https://chromium-review.googlesource.com/c/chromium/src/+/1171789

[CrOS MultiDevice] Add FeatureStateManager.

This class determines the active state of each multi-device feature. A
future CL will integrate this class with the MultiDeviceSetup service
so that the settings page as well as each individual feature can query
the service for the correct state to show in the UI.


(2) https://chromium-review.googlesource.com/c/chromium/src/+/1172707

[CrOS MultiDevice] Add feature state management to MultiDeviceSetup.

This CL adds a new set of APIs for getting/setting the states of the
multi-device features as well as adding an observer pattern for
receiving updates to these feature states.


(3) https://chromium-review.googlesource.com/c/chromium/src/+/1173653

[CrOS MultiDevice] Update MultiDeviceSetupClient w/ feature APIs.

This CL adds SetFeatureEnabledState() and GetFeatureState() functions to
MultiDeviceSetupClient.


(4) https://chromium-review.googlesource.com/c/chromium/src/+/1176658

[CrOS MultiDevice] Send feature states to MultiDevice settings handler.

This CL updates MultideviceHandler to provide the settings page with the
state of all multi-device features.

Note that this CL uses the MultiDevicePageContentData definition from
https://chromium-review.googlesource.com/c/chromium/src/+/1173658 when
passing its data, so these CLs should be landed at the ~same time.


(5) https://chromium-review.googlesource.com/c/chromium/src/+/1176870

[CrOS MultiDevice] Add setFeatureStateEnabled() to MultiDevice proxy.

This allows the settings page to request that multi-device features be
enabled or disabled via clicks on a toggle.