[Android] Use interceptor to handle assets for shared mode

Therefore, we can get rid of the change in chromium to revert
r258491 to use library Context in ResourceExtractor.java.

BUG=https://crosswalk-project.org/jira/browse/XWALK-2575
Merge pull request #2448 from wang16/appctx_for_resource_extractor

[Android] Use interceptor to handle assets for shared mode