Reduce size of second iteration in SkTileGridNextDatum<>().
Reduce size of second iteration in SkTileGridNextDatum<>().

Rather than iterating over the entire dataset twice, during the first pass
track how large the second pass needs to be. Entirely data-dependent but
in practice approaches 2x speedup.

BUG=1212
R=junov
https://codereview.appspot.com/8315044/



git-svn-id: e8541e15acce502a64c929015570ad1648e548cd@8543 2bbb7eff-a529-9590-31e7-b0007b416f81

Frankie-666/color-emoji.skia,Hankuo/color-emoji.skia,hbwhlklive/color-emoji.skia,hbwhlklive/color-emoji.skia,Hankuo/color-emoji.skia,Hankuo/color-emoji.skia,Frankie-666/color-emoji.skia,Hankuo/color-emoji.skia,MatChung/color-emoji.skia,Frankie-666/color-emoji.skia,MatChung/color-emoji.skia,MatChung/color-emoji.skia,hbwhlklive/color-emoji.skia,MatChung/color-emoji.skia,MatChung/color-emoji.skia,Hankuo/color-emoji.skia,Frankie-666/color-emoji.skia,Hankuo/color-emoji.skia,Frankie-666/color-emoji.skia,MatChung/color-emoji.skia,hbwhlklive/color-emoji.skia,hbwhlklive/color-emoji.skia,hbwhlklive/color-emoji.skia,Frankie-666/color-emoji.skia