Update AndroidNetworkLibrary getSSID function to handle lack of permissions.

getSSID on Android may return a special pre-defined string if the app
does not have permissions to get the SSID.

In that case, the method returns an empty string.

Change-Id: I58c99301b4d611124c8434e93fd787edbec32da3
Bug: 827212
Reviewed-on: https://chromium-review.googlesource.com/987306Reviewed-by: Paul Jensen <pauljensen@chromium.org>
Commit-Queue: Tarun Bansal <tbansal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#548650}

net/android/java/src/org/chromium/net/AndroidNetworkLibrary.java

@@ -213,8 +213,11 @@ class AndroidNetworkLibrary {
     }
 
     /**
-     * Gets the SSID of the currently associated WiFi access point if there is one. Otherwise,
-     * returns empty string.
+     * Gets the SSID of the currently associated WiFi access point if there is one, and it is
+     * available. SSID may not be available if the app does not have permissions to access it. On
+     * Android M+, the app accessing SSID needs to have ACCESS_COARSE_LOCATION or
+     * ACCESS_FINE_LOCATION. If there is no WiFi access point or its SSID is unavailable, an empty
+     * string is returned.
      */
     @CalledByNative
     public static String getWifiSSID() {
@@ -224,7 +227,9 @@ class AndroidNetworkLibrary {
             final WifiInfo wifiInfo = intent.getParcelableExtra(WifiManager.EXTRA_WIFI_INFO);
             if (wifiInfo != null) {
                 final String ssid = wifiInfo.getSSID();
-                if (ssid != null) {
+                // On Android M+, the platform APIs may return "<unknown ssid>" as the SSID if the
+                // app does not have sufficient permissions. In that case, return an empty string.
+                if (ssid != null && !ssid.equals("<unknown ssid>")) {
                     return ssid;
                 }
             }

net/android/network_library.h

@@ -77,8 +77,11 @@ NET_EXPORT bool GetIsRoaming();
 // Marshmallow and later versions. Returns false on earlier versions.
 NET_EXPORT bool GetIsCaptivePortal();
 
-// Gets the SSID of the currently associated WiFi access point if there is one.
-// Otherwise, returns empty string.
+// Gets the SSID of the currently associated WiFi access point if there is one,
+// and it is available. SSID may not be available if the app does not have
+// permissions to access it. On Android M+, the app accessing SSID needs to have
+// ACCESS_COARSE_LOCATION or ACCESS_FINE_LOCATION. If there is no WiFi access
+// point or its SSID is unavailable, an empty string is returned.
 NET_EXPORT_PRIVATE std::string GetWifiSSID();
 
 // Gets the DNS servers and puts them in |dns_servers|.

net/base/network_interfaces.h

@@ -86,8 +86,11 @@ enum HostAddressSelectionPolicy {
 NET_EXPORT bool GetNetworkList(NetworkInterfaceList* networks,
                                int policy);
 
-// Gets the SSID of the currently associated WiFi access point if there is one.
-// Otherwise, returns empty string.
+// Gets the SSID of the currently associated WiFi access point if there is one,
+// and it is available. SSID may not be available if the app does not have
+// permissions to access it. On Android M+, the app accessing SSID needs to have
+// ACCESS_COARSE_LOCATION or ACCESS_FINE_LOCATION. If there is no WiFi access
+// point or its SSID is unavailable, an empty string is returned.
 // Currently only implemented on Linux, ChromeOS, Android and Windows.
 NET_EXPORT std::string GetWifiSSID();