Fix minor TimingFunction validation issue

[marcelgerber]

This fixes a rather uncommon issue in TimingFunction validation. Steps:

1. Try to open an Inline Editor on animation-timing-function: cubic-bezier(0, 0, 0, 0,) (notice the trailing comma)

Result: Console error, no inline editor
Expected: Inline editor should auto-correct the invalid function

[redmunds]

@marcelgerber This is an interesting case. Due to the regex used to parse the cubic-bezier string, the last value is "everything past the 3rd comma and past whitespace". So there could be a lot of weird stuff in here -- too much I think to try to parse with our own regex.

So, I looked at the code that currently traps the exception and it's using the unary operator to convert from string to number. I think we still need parseFloat to make sure it's a base 10 number, but this code seems to be simpler, solve the problem, and all unit tests still work:

        if (typeof str !== "string") {
            return { isNumber: false, value: null };
        }

        var val = parseFloat(+str, 10),
            isNum = (typeof val === "number") && !isNaN(val) &&
                    (val !== Infinity) && (val !== -Infinity);

What do you think of this solution?

[redmunds]

Code review complete. I think this can be solved without a new regex.

[marcelgerber]

@redmunds Your solution works well, therefore I used it.

[redmunds]

Yay! Unit test!

[redmunds]

Good catch. Merging.