mozilla/pdf.js — pull request #5172 by nnethercote (2014-08-12 04:21:57+00:00)
Title: Avoid an allocation in readCharCode().

readCharCode() returns two values, and currently allocates a length-2
array on every call to do so. This change makes it instead us a
passed-in object which can be reused.

This tiny change reduces the total JS allocations done for the document
in Mozilla bug 992125 by 4.2%.