[Android] Fix the crash issue of loading app from app:// scheme

As the resource rquest URL was canonicalized to lowercase by core,
the host name exacted from the URL may be inconsitent with the app
package name, if there is captical capital letter in the package
name. So convert package name to lowercase before comparing these
2 strings.

BUG=https://crosswalk-project.org/jira/browse/XWALK-808