Implement Networking Private API VerifyAndEncryptCredentials method

components/wifi/fake_wifi_service.cc

Index: components/wifi/fake_wifi_service.cc
diff --git a/components/wifi/fake_wifi_service.cc b/components/wifi/fake_wifi_service.cc
index af78d72bffc0324e801b2deb83ca0c0397e26e8f..3330046772d9d1b43b04a140919ab8b6d68367b0 100644
--- a/components/wifi/fake_wifi_service.cc
+++ b/components/wifi/fake_wifi_service.cc
@@ -254,6 +254,12 @@ class FakeWiFiService : public WiFiService {
     }
   }
 
+  virtual void GetPassphraseFromSystem(const std::string& network_guid,
+                                       std::string* passphrase,
+                                       std::string* error) OVERRIDE {
+    *error = "not-found";
+  }
+
   virtual void SetEventObservers(
       scoped_refptr<base::MessageLoopProxy> message_loop_proxy,
       const NetworkGuidListCallback& networks_changed_observer,