[Android] Fix the missing files issue in xwalk_core_library of M34

After rebasing to M34, xwalk_core_library needs several additional Java
source files to pass the build.

BUG=https://crosswalk-project.org/jira/browse/XWALK-1019
Merge pull request #1615 from huningxin/fix_core_library

[Android] Fix the missing files issue in xwalk_core_library of M34