Correct glyph with non-bmp from typeface on Mac.

Correct glyph with non-bmp from typeface on Mac.

CTFontGetGlyphsForChars puts the glyph id at the index of the lead
surrogate as is documented in comments, but the code is looking at
the index of the trail surrogate.

BUG=skia:2960
Committed: https://skia.googlesource.com/skia/+/7b09aab7130c174c6a2dd4becedbddaa6cf7945d

[bungeman-skia, 2014-09-24 17:42:19]

bungeman@google.com changed reviewers:
+ mtklein@google.com

[bungeman-skia, 2014-09-24 17:42:20]

The testing for this sort of thing is mostly around
SkScalerContext::generateCharToGlyph instead of SkTypeface::onCharsToGlyphs
(since generateCharToGlyph existed first). The idea was to test the one (and
generateCharToGlyph does work correctly) and then make sure that the other gave
the same output. However, while the test was written correctly, we haven't
actually been running the test with fonts which actually contain non-bmp
character mappings. The test has been changed to do so, and with this test
change there is a failure with the old code which is fixed by the new.

[mtklein, 2014-09-24 17:49:58]

The CQ bit was checked by mtklein@google.com

[mtklein, 2014-09-24 17:49:58]

lgtm

[commit-bot: I haz the power, 2014-09-24 17:50:31]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/596413002/1

[commit-bot: I haz the power, 2014-09-24 18:04:44]

Committed patchset #1 (id:1) as 7b09aab7130c174c6a2dd4becedbddaa6cf7945d