[Android] Aligh with new java targets' classes_dir

Chromium has changed java targets' classes_dir to
<intermediate>/classes/2.
It impacts xwalk_native_libraries_java and
xwalk_core_library_java in crosswalk. Changes the
classes_dir of these two targets accordingly.

In addition, use dependent settings of gyp to sync variables
between targets instead of hardcode to avoid similar issues in
future.
[Android] Update screen orientation's test case per spec

Spec changes the API namespace from "window.screen" to
"screen.orientation", update the test cases accordingly.