adding unit test for textblob cache / GrBatchAtlas
adding unit test for textblob cache / GrBatchAtlas

BUG=skia:

Review URL: https://codereview.chromium.org/1233253003

nvoron23/skia,todotodoo/skia,ominux/skia,HalCanary/skia-hc,google/skia,noselhq/skia,Hikari-no-Tenshi/android_external_skia,nvoron23/skia,qrealka/skia-hc,aosp-mirror/platform_external_skia,noselhq/skia,google/skia,nvoron23/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,tmpvar/skia.cc,aosp-mirror/platform_external_skia,noselhq/skia,qrealka/skia-hc,google/skia,aosp-mirror/platform_external_skia,tmpvar/skia.cc,noselhq/skia,tmpvar/skia.cc,vanish87/skia,todotodoo/skia,google/skia,nvoron23/skia,google/skia,shahrzadmn/skia,nvoron23/skia,google/skia,ominux/skia,Hikari-no-Tenshi/android_external_skia,vanish87/skia,Hikari-no-Tenshi/android_external_skia,nvoron23/skia,ominux/skia,rubenvb/skia,vanish87/skia,aosp-mirror/platform_external_skia,vanish87/skia,ominux/skia,shahrzadmn/skia,noselhq/skia,rubenvb/skia,qrealka/skia-hc,HalCanary/skia-hc,qrealka/skia-hc,rubenvb/skia,rubenvb/skia,nvoron23/skia,qrealka/skia-hc,rubenvb/skia,aosp-mirror/platform_external_skia,rubenvb/skia,nvoron23/skia,ominux/skia,ominux/skia,noselhq/skia,HalCanary/skia-hc,todotodoo/skia,google/skia,HalCanary/skia-hc,ominux/skia,HalCanary/skia-hc,Hikari-no-Tenshi/android_external_skia,todotodoo/skia,qrealka/skia-hc,ominux/skia,aosp-mirror/platform_external_skia,shahrzadmn/skia,tmpvar/skia.cc,vanish87/skia,vanish87/skia,shahrzadmn/skia,tmpvar/skia.cc,google/skia,rubenvb/skia,rubenvb/skia,rubenvb/skia,vanish87/skia,vanish87/skia,ominux/skia,HalCanary/skia-hc,nvoron23/skia,google/skia,google/skia,tmpvar/skia.cc,shahrzadmn/skia,rubenvb/skia,noselhq/skia,Hikari-no-Tenshi/android_external_skia,noselhq/skia,tmpvar/skia.cc,shahrzadmn/skia,Hikari-no-Tenshi/android_external_skia,aosp-mirror/platform_external_skia,HalCanary/skia-hc,shahrzadmn/skia,Hikari-no-Tenshi/android_external_skia,Hikari-no-Tenshi/android_external_skia,tmpvar/skia.cc,noselhq/skia,aosp-mirror/platform_external_skia,tmpvar/skia.cc,HalCanary/skia-hc,todotodoo/skia,todotodoo/skia,shahrzadmn/skia,qrealka/skia-hc,shahrzadmn/skia,todotodoo/skia,todotodoo/skia,HalCanary/skia-hc,todotodoo/skia,vanish87/skia,qrealka/skia-hc,HalCanary/skia-hc