Bug 889016 - Part 1: Add an API to report a not-enough-arguments error in Web IDL bindings; r=bzbarsky a=bajaj

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Bug 889016 - Part 2: Report an error in the synchronous AudioContext.createBuffer unless the legacy pref has been set; r=roc a=webaudio

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extra : transplant_source : %BC%99%F6%8F%89Fn%81%D4%BA%7C%1B%A7%C9%EE%21%8A%AC%DB%10