[webapi] Automate 14 tests for CSS3 multicolumn as reftest.

Impacted TCs num(approved): New 0, Update 14, Delete 0
Unit test Platform: [Andriod]
Unit test result summary: Pass 14, Fail 0, blocked 0
Please don't use multi-column properties when create reference files for multi-column properties test cases.

See http://testthewebforward.org/docs/reftests.html#2-the-reftest-reference-file

> The reference file must not use the same features that are being tested, but uses a different method to produce the same rendering as a test file. Sometimes more than one reference file is required.