use ParagraphStyle's fHintingIsOn flag when typesetting

[samizdatco]

The ParagraphStyle struct has as turnHintingOff() setter which toggles its fHintingIsOn flag, but this flag is never read when the paragraph is typeset. As a result, hinting is always enabled regardless of the ParagraphStyle’s settings.

This PR adds a check for hinting having been disabled at the ParagraphStyle level and only defers to the Block's hinting setting if it is enabled.

Note: it's not entirely clear to me that this is the proper (or only) location for this flag to be honored, but having the ability to disable hinting at the ParagraphStyle level is an important feature (since direct access to the Font objects used is unavailable when typesetting paragraphs rather than TextBlobs). It's also a feature that the existing API suggests exists, while currently it has no effect.

[skia-codereview-bot]

This PR (HEAD: 58e8c05) has been imported to Gerrit for code review.

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