Don't purge resources from cache if they have > 1 ref
Don't purge resources from cache if they have > 1 ref

https://codereview.appspot.com/6494069/



git-svn-id: e8541e15acce502a64c929015570ad1648e548cd@5380 2bbb7eff-a529-9590-31e7-b0007b416f81

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