Excellent question! Yes, Chrome uses the Webkit rendering engine, but Google came at a lot of these things from the opposite direction, their apps. For example, do you remember Google Gears, and how it then kind of disappeared? That's because they uses Gears to implement a lot of the stuff that because application support in HTML5, and when HTML5 got it, they could dump Gears. So a lot of it was in the API levels, above the rendering engine.
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