Enhance portal check code to return connectivity_state

doc/service-api.txt

 Service hierarchy
 =================
 
 Service         org.chromium.flimflam
 Interface       org.chromium.flimflam.Service
 Object path     [variable prefix]/{service0,service1,...}
 
 Methods         dict GetProperties()
 
                         Returns properties for the service object. See
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                         This property is included in get requests only
                         when the requester has sufficient privileges.
 
                 string AuthorityPath [readwrite]
 
                         If the service type is "wifi", then this
                         property holds information that selects a
                         certificate authority file for use in validating
                         server certificate recieved from the access point
                         during the 802.1x authentication process.
-                        
+
+                string ConnectivityState [readonly]
+                        This property indicates whether the data
+                        connection is within a "walled garden", in
+                        which only a restricted set of IP addresses
+                        can be reached. A value of "restricted"
+                        indicates that the connection is in such a
+                        restricted IP pool.  A value of "unrestricted"
+                        indicates that the connection has unrestricted
+                        access to the internet, and a value of "none"
+                        means that it is unlikely that any internet
+                        access is available, despite having obtained
+                        an IP address.
+
+                        This property is only valid when the service
+                        is the default service and is in the "ready"
+                        state.  The default value is "unknown",
+                        changing to "restricted", "unrestricted" or
+                        "none" after enough time (~5 seconds after
+                        becoming the default service) has elapsed to
+                        establish the state of IP connectivity.
+
+                        This state is currently only computed for
+                        services of type Cellular, but it can be made
+                        applicable to other services types.
+
                 boolean PassphraseRequired [readonly]
 
                         If the service type is "wifi", then this property
                         indicates if a passphrase or key (for WEP) is required.
 
                         If a passphrase has been set already or if no
                         passphrase is needed, then this property will
                         be set to false.
 
                         UI clients may monitor this property for a
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                         "LTE"          3.9G
                         "LTE Advanced" 4G
 
                 string Cellular.RoamingState [readonly]
 
                         If the service type is "cellular", then this property
                         gives the roaming status of the modem on the current
                         network. Possible values are "home", "roaming", and
                         "unknown".
 
-                boolean Cellular.RestrictedPool [readonly]
-                        If the service type is "cellular", then this property
-                        indicates whether the mobile data connection is within
-                        a "walled garden", in which only a restricted set of
-                        IP addresses can be reached. A value of "true" indicates
-                        that the connection is in a restricted IP
-                        pool.
-
-                        This property is only valid when the service
-                        is in the "ready" state.  The default value is
-                        "false", only changing to "true" after enough
-                        time (~5 seconds after becoming the default
-                        service) has elapsed to assume that the IP
-                        connectivity is restricted.
-
                 string Cellular.OlpUrl [readonly]
 
                         If the service type is "cellular", then this property
                         gives the URL of an online payment portal (OLP) at
                         which a user can sign up for, or modify, a mobile data
                         plan.
 
                 string Passphrase [readwrite]
 
                         If the service type is "wifi", then this property
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                         gives the 802.1X Certificate Authority Path.
                         
                         This property is only accessible if the caller has 
                         'secret' security privileges. 
 
                 string PassphraseRequired [readonly]
 
                         If the service type is "wifi", then this property
                         indicates that a Passphrase is required but not
                         currently set.