Refactor tests.

Change-Id: Ie35779533b8dda19e1c7d1d408ffeba2574a8757
Signed-off-by: Wei-Chung Wen <morisato3711@gmail.com>
Implement more unit tests for class BookmarkSync.

Change-Id: I266fd562fdaaa88f338d76cf0e1264e5ebe7ba23
Signed-off-by: Wei-Chung Wen <morisato3711@gmail.com>