Avoid unnecessary comparison if both Typeface are NULL
Avoid unnecessary comparison if both Typeface are NULL

BUG=skia:

Review URL: https://codereview.chromium.org/1177833004

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