Auto merge of #2262 - lsalzman:italics-hinting-fix, r=jrmuizel
Auto merge of #2262 - lsalzman:italics-hinting-fix, r=jrmuizel

Fix FreeType synthetic italics hinting

This is a follow-up to #2245. In certain cases with skew matrices and/or disable anti-aliasing, the apparent weight and offsetting of the font will significantly differ from Gecko, causing some reftests to fail. These changes ensure that we match Gecko which has the beneficial side-effect that not only do the synthetic italics reftests pass, but a few other WebRender related failures are fixed as well.

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