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The HarfBuzz roll in r513541 improved Mac UI font support in the
renderer by detecting UI fonts and invoking CTFontCreateUIFontForLanguage().

However, in chrome UI, there is already a CTFont wrapped in a gfx::
PlatformFont for UI fonts. So creating a new CTFont for every hb_shape
call becomes unnecessary and expensive.

hb_coretext_font_create() (after a hb_coretext_face_create()) allows
the steps requiring the call to CTFontCreateUIFontForLanguage() to
be skipped by associating the CTFont with the hb_font_t directly.

Adds a new views_perftest target and LabelPerfTest.GetPreferredSize
to track. On a Late 2013 Mac Pro perf improves from 1390 runs/second
to 3300 runs/second.

+250 runs/second of that comes from a related hotspot in gfx::internal::
CreateSkiaTypeface() which was deriving a new CTFont unnecessarily
before sending it to gfx::CreateHarfBuzzFont().

Bug: 785522
Change-Id: Iccf57fe3fc9a93cd4b9de1e79e81fb84d2ad88bb
Reviewed-on: https://chromium-review.googlesource.com/823743
Commit-Queue: Trent Apted <tapted@chromium.org>
Reviewed-by: Michael Wasserman <msw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#526920}