You can enable WebGL in Safari. Go to Preferences -> Advanced and click "Show Develop menu in menubar". "Enable WebGL" is the last item in the Develop menu.
There has been a very obvious Chrome|Safari|Webkit only trend recently, usually for either demos/pocs, but also often for MVP/betas (I believe Mega may have been one of those).
The actual function being plotted is the two ellipsoids
1 = x^2 + (x - y)^2 + z^2 for x >= 0
1 = x^2 + (x + y)^2 + z^2 for x <= 0
Each of which which is just an ordinary ellipse but rotated a little along the z-axis. If you expand the square and by standard linear algebra techniques (see: diagonalising a quadratic form), you can put both of these in standard form:
1 = x^2/a^2 + y^2/b^2 + z^2
which confirms it's an ellipsoid.
Whoever made the original heart just took these two ellipses and then multiplied by the cosine of the height in order to give it some oscillations and make it look more showy, but the basic idea is just that: two ellipsoids, at opposite slant angles, joined along the middle.
The OP din't claim to have created this (although arguably it's implied by it's posting without comment). Rather, that's just one of quite a number of such functions posted here before. I don't know their origin.
So well done for remembering it, and reposting it on an appropriate day; or more likely someone else remembered, and this is just a cross-post of a cross-post of a blog of a re-post. But well done anyway.
http://www.wolframalpha.com/input/?i=Plot%5BSqrt%5BCos%5Bx%5...