UMA histogram to measure the time OTS takes to decode a webfont
UMA histogram to measure the time OTS takes to decode a webfont

This adds WebFont.DecodeSpeed.* histograms that record the rate at which
OTS decodes a webfont to uncompressed format.

BUG=447127

Review URL: https://codereview.chromium.org/842913004

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@188440 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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