Need more calc() tests

[yoavweiss]

I've got the threadsafe calc() impl working , and added a bunch of tests, but many more are needed.

[Wilto]

Here are the cases we have so far:

TestCase testCases[] = {
        {"calc(500px + 10em)", 660},
        {"calc(500px + 2 * 10em)", 820},
        {"calc(500px + 2*10em)", 820},
        {"calc(500px + 50%*10em)", 580},
        {"calc(500px + (50%*10em + 13px))", 593},
        {"calc(100vw + (50%*10em + 13px))", 593},
        {"calc(100vh + (50%*10em + 13px))", 736},
        {0, 0} // Do not remove the terminator line.
    };