[webkit-reviews] review requested: [Bug 31802] Switch Chrome on Mac to Core Text APIs : [Attachment 44468] Add optional ATSUI/Core Text runtime switch.

[bugzilla-daemon at webkit.org]

Jeremy Moskovich <playmobil at google.com> has asked  for review:
Bug 31802: Switch Chrome on Mac to Core Text APIs
https://bugs.webkit.org/show_bug.cgi?id=31802

Attachment 44468: Add optional ATSUI/Core Text runtime switch.
https://bugs.webkit.org/attachment.cgi?id=44468&action=review

------- Additional Comments from Jeremy Moskovich <playmobil at google.com>
We observed the slowdown Dan was referring to on the Chrome perf bots and
rolled back the previous patch.

This patch adds the ability to define both USE(ATSUI) and USE(CORE_TEXT) in
which case the API is toggled at runtime.  If a port defines only one of these,
things should work exactly as they do today.

I made sure that indexAt() and collectComplexTextRunsForCharacters() are indeed
inlined by the compiler so there should be virtually no runtime hit for this
patch.