[Android] Fix resId setting for internal resources failed

Previously, Field.isAccessible() is used to detect whether
the field is final. It's wrong in java reflection.
Fix it by using Modifier.isFinal(getModifers()) instead.

BUG=https://crosswalk-project.org/jira/browse/XWALK-1115
Merge pull request #1676 from wang16/fix_res_final

[Android] Fix resId setting for internal resources failed