Add method GetKeyFromSystem to WiFiService on Windows and Mac.

components/wifi/wifi_service.h

Index: components/wifi/wifi_service.h
diff --git a/components/wifi/wifi_service.h b/components/wifi/wifi_service.h
index f7e7999fa8ac35ae37eeb2b6a391dca3f6831855..10b63775e92d13a192672637bfa5017b50c3d665 100644
--- a/components/wifi/wifi_service.h
+++ b/components/wifi/wifi_service.h
@@ -100,6 +100,15 @@ class WIFI_EXPORT WiFiService {
   virtual void StartDisconnect(const std::string& network_guid,
                                std::string* error) = 0;
 
+  // Get WiFi Key for network identified by |network_guid| from the
+  // system (if it has one) and store it in |key_data|. If |get_plaintext_key|
+  // is |true|, then user privilege elevation may be required, and function will
+  // fail if user privileges are not sufficient. Populates |error| on failure.
+  virtual void GetKeyFromSystem(const std::string& network_guid,
+                                bool get_plaintext_key,
+                                std::string* key_data,
+                                std::string* error) = 0;
+
   // Set observers to run when |NetworksChanged| and |NetworksListChanged|
   // events needs to be sent. Notifications are posted on |message_loop_proxy|.
   virtual void SetEventObservers(