[Content] TCT fixes

Improve Tizen Compliancy Test (TCT) suite pass rates:

  - Implement missing updateBatch method
  - Check for null and range assignments for js objects

BUG=XWALK-2801
BUG=XWALK-2802
BUG=XWALK-2808
BUG=XWALK-2811
const_iterator?