Hide password for wifi tether

Add summaryPassword variable in ValidatedEditTextPreference. If it
is true, set the summary textview with password flag.

Bug: 65413204
Test: RunSettingsRoboTests
Change-Id: Ia0f1e3ab50e81d8f7f9fc0fb34b35c3041200a4e

src/com/android/settings/wifi/tether/WifiTetherPasswordPreferenceController.java

@@ -51,6 +51,7 @@ public class WifiTetherPasswordPreferenceController extends WifiTetherBasePrefer
             Log.d(TAG, "Updating password in Preference, " + mPassword);
         }
         ((ValidatedEditTextPreference) mPreference).setValidator(this);
+        ((ValidatedEditTextPreference) mPreference).setIsSummaryPassword(true);
         updatePasswordDisplay((EditTextPreference) mPreference);
     }