Protect GrantCredentialsPermissionActivity against overlay.

Bug: 169763814
Test: manual
Merged-In: I15dd22791fcc61ef02b06ad51d9e4409d11c0181
Change-Id: I0d8f901d100a5e2a022c96fa6c2be75a11c58059

core/java/android/accounts/GrantCredentialsPermissionActivity.java

@@ -55,6 +55,9 @@ public class GrantCredentialsPermissionActivity extends Activity implements View
 
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
+        getWindow().addPrivateFlags(
+                android.view.WindowManager.LayoutParams
+                        .PRIVATE_FLAG_HIDE_NON_SYSTEM_OVERLAY_WINDOWS);
         setContentView(R.layout.grant_credentials_permission);
         setTitle(R.string.grant_permissions_header_text);