[CrOS Tether] Add the notion of a tether DeviceState.

chromeos/network/network_state_handler.h

Index: chromeos/network/network_state_handler.h
diff --git a/chromeos/network/network_state_handler.h b/chromeos/network/network_state_handler.h
index 3265b00141c167c6fb162db3ff6a8bcd7cd1ba88..6fc19b4e26fd652c6a5f7ec640714623ed300446 100644
--- a/chromeos/network/network_state_handler.h
+++ b/chromeos/network/network_state_handler.h
@@ -112,6 +112,17 @@ class CHROMEOS_EXPORT NetworkStateHandler
       bool enabled,
       const network_handler::ErrorCallback& error_callback);
 
+  // Sets the tether technology state. Because Tether networks do not represent
+  // real Shill networks, this value must be set by the tether component rather
+  // than being generated by Shill. See TetherDeviceStateManager for more
+  // details.
+  void SetTetherTechnologyState(TechnologyState technology_state);
+
+  // Sets the scanning state of the tether technology. Since tether network
+  // scans are not actually performed as part of Shill, this value must be set
+  // by the tether component.
+  void SetTetherScanState(bool is_scanning);
+
   // Asynchronously sets the list of prohibited technologies. The accepted
   // values are the shill network technology identifiers. See also
   // chromeos::onc::Validator::ValidateGlobalNetworkConfiguration().
@@ -250,7 +261,11 @@ class CHROMEOS_EXPORT NetworkStateHandler
                            DeviceStateList* list) const;
 
   // Requests a network scan. This may trigger updates to the network
-  // list, which will trigger the appropriate observer calls.
+  // list, which will trigger the appropriate observer calls. Note that this
+  // function does not request a tether scan.
+  // TODO(khorimoto): Add an also_scan_for_tether parameter. Tether scans should
+  // not occur during start-up, but they should occur when opening networking
+  // UI.

[stevenjb, 2017/04/20 16:49:42]

I don't think we should put that logic in the startup / UI code. Instead, this
method should trigger a scan request to the tether code which it is free to
ignore. i.e. this function is a 'request', not a directive.

[Kyle Horimoto, 2017/04/20 19:38:46]

Done.

   void RequestScan() const;
 
   // Requests an update for an existing NetworkState, e.g. after configuring
@@ -259,7 +274,7 @@ class CHROMEOS_EXPORT NetworkStateHandler
   // acknowledged it (e.g. in the callback of a SetProperties).
   // When the properties are received, NetworkPropertiesUpdated will be
   // signaled for each member of |observers_|, regardless of whether any
-  // properties actually changed.
+  // properties actually changed. Note that this is a no-op for Tether networks.
   void RequestUpdateForNetwork(const std::string& service_path);
 
   // Informs NetworkStateHandler to notify observers that the properties for
@@ -482,6 +497,12 @@ class CHROMEOS_EXPORT NetworkStateHandler
   // NetworkState that is not saved in a profile.
   SpecifierGuidMap specifier_guid_map_;
 
+  // The state corresponding to the tether device type. Initialized to
+  // PROHIBITED; this value is changed by the tether component when it starts
+  // up.

[stevenjb, 2017/04/20 16:49:42]

nit: s/is changed by the tether component when it starts up/is managed by the
tether component/

[Kyle Horimoto, 2017/04/20 19:38:46]

Done.

+  TechnologyState tether_technology_state_ =
+      TechnologyState::TECHNOLOGY_PROHIBITED;

[stevenjb, 2017/04/20 18:29:07]

This should be initialized to UNAVAILABLE which should also indicate that no
DeviceState for Tether exists. i.e. this is equivalent to NSH and Chrome not
having any awareness of Tether. We should rely on SetTetherTechnologyState()
getting called with something other than UNAVAILABLE to create a DeviceState.
(This should only be set to PROHIBITED by policy code).

[Kyle Horimoto, 2017/04/20 19:38:46]

Done.

+
   // Ensure that Shutdown() gets called exactly once.
   bool did_shutdown_ = false;