[Android] Fix white screen issue when load http.html with manifest.

Correct the judgment of url schemes in xwalk_content.cc.

BUG=https://crosswalk-project.org/jira/browse/XWALK-985
(cherry picked from commit b140aecdcfff652ea6e72b5ce2d1a2c48e20930d)
Merge pull request #1775 from gaochun/crosswalk-5

[Android] Fix white screen issue when load http.html with manifest.