[Android] Use render frame to retrieve web contents for some cases.

Chromium uses render frame for some cases instead of render view. This
change tries to follow up the behaviors defined by upstream.

BUG=https://crosswalk-project.org/jira/browse/XWALK-1252
Merge pull request #1730 from yongsheng/fix1252

[Android] Use render frame to retrieve web contents.