[Android] Enable ssl connection with untrusted certificate.

If the server has an untrusted certificate, nothing will be displayed in
current implementation. Enable to allow certification error by showing a
dialog to users to decide whether to accept it.
Need a test case from QA to verify it.

BUG=https://crosswalk-project.org/jira/browse/XWALK-1246
Merge pull request #1736 from yongsheng/xwalk1246

[Android] Enable ssl connection with untrusted certificate.