* Add calc method to calculate formula value with parent size
* Add unit test case
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Please see this issue: https://github.com/servo/servo/issues/15986
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- [x] These changes fix#15986 (github issue number if applicable).
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Source-Repo: https://github.com/servo/servo
Source-Revision: 418c3e8cc74b561c9c704da4dfdfb74681bf42a1
--HG--
extra : subtree_source : https%3A//hg.mozilla.org/projects/converted-servo-linear
extra : subtree_revision : 1d48fb23022078c51f68df824ef6b0501c81b8cb
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