[webapi] Add 30 tests for colors from csswg

- These tests come from https://github.com/w3c/csswg-test/tree/master/css-color-3 (commit 1b4be5f723b43e723db9493abdd743eca0e3f5e8)
- Update xht files to htm file

Impacted tests(approved): new 30, update 0, delete 0
Unit test platform: [android] crosswalk-10.38.222
Unit test result summary: pass 30, fail 0, block 0
Merge pull request #1357 from xinliux/colors-upstream

[webapi] Add 30 tests for colors from csswg