[Android] Fix the issue of accessing asset resources with unnormalized URI.

Web applications may have unnormalized URI (additional slashes), which causes
failure of accessing them with AndroidProtocolHandler.
The fix was in Crosswalk, but https://github.com/crosswalk-project/crosswalk/commit/12b98a890de27d1ec96eb7f10558010fc7412e58
reverts it. So moving it back.

BUG=https://crosswalk-project.org/jira/browse/XWALK-2226
Merge pull request #2279 from sqliu/fix-asset

[Android] Fix the issue of accessing asset resources with unnormalized U...