Make writeRenderTargetPixels use draw buffer rather than GrGpu
Make writeRenderTargetPixels use draw buffer rather than GrGpu

R=robertphillips@google.com

Author: bsalomon@google.com

Review URL: https://codereview.chromium.org/586393005

aosp-mirror/platform_external_skia,google/skia,YUPlayGodDev/platform_external_skia,OneRom/external_skia,invisiblek/android_external_skia,timduru/platform-external-skia,geekboxzone/mmallow_external_skia,MinimalOS-AOSP/platform_external_skia,VRToxin-AOSP/android_external_skia,w3nd1go/android_external_skia,Jichao/skia,nvoron23/skia,chenlian2015/skia_from_google,rubenvb/skia,rubenvb/skia,MinimalOS-AOSP/platform_external_skia,boulzordev/android_external_skia,nfxosp/platform_external_skia,timduru/platform-external-skia,boulzordev/android_external_skia,HalCanary/skia-hc,timduru/platform-external-skia,Infinitive-OS/platform_external_skia,rubenvb/skia,scroggo/skia,pcwalton/skia,MarshedOut/android_external_skia,AOSP-YU/platform_external_skia,todotodoo/skia,aosp-mirror/platform_external_skia,chenlian2015/skia_from_google,invisiblek/android_external_skia,invisiblek/android_external_skia,jtg-gg/skia,invisiblek/android_external_skia,YUPlayGodDev/platform_external_skia,ominux/skia,BrokenROM/external_skia,MinimalOS-AOSP/platform_external_skia,TeamTwisted/external_skia,rubenvb/skia,noselhq/skia,jtg-gg/skia,OneRom/external_skia,UBERMALLOW/external_skia,nvoron23/skia,nfxosp/platform_external_skia,AOSP-YU/platform_external_skia,tmpvar/skia.cc,OneRom/external_skia,Igalia/skia,TeamTwisted/external_skia,YUPlayGodDev/platform_external_skia,MarshedOut/android_external_skia,MonkeyZZZZ/platform_external_skia,vanish87/skia,AOSP-YU/platform_external_skia,OneRom/external_skia,HalCanary/skia-hc,google/skia,geekboxzone/mmallow_external_skia,amyvmiwei/skia,VRToxin-AOSP/android_external_skia,rubenvb/skia,rubenvb/skia,Jichao/skia,MonkeyZZZZ/platform_external_skia,AOSP-YU/platform_external_skia,rubenvb/skia,w3nd1go/android_external_skia,VRToxin-AOSP/android_external_skia,Igalia/skia,samuelig/skia,PAC-ROM/android_external_skia,OneRom/external_skia,timduru/platform-external-skia,nfxosp/platform_external_skia,w3nd1go/android_external_skia,Infinitive-OS/platform_external_skia,MonkeyZZZZ/platform_external_skia,tmpvar/skia.cc,Hikari-no-Tenshi/android_external_skia,HalCanary/skia-hc,todotodoo/skia,AOSPB/external_skia,PAC-ROM/android_external_skia,boulzordev/android_external_skia,TeamExodus/external_skia,PAC-ROM/android_external_skia,TeamExodus/external_skia,google/skia,boulzordev/android_external_skia,pcwalton/skia,aosp-mirror/platform_external_skia,timduru/platform-external-skia,todotodoo/skia,Jichao/skia,MonkeyZZZZ/platform_external_skia,BrokenROM/external_skia,aosp-mirror/platform_external_skia,scroggo/skia,geekboxzone/mmallow_external_skia,HalCanary/skia-hc,UBERMALLOW/external_skia,google/skia,qrealka/skia-hc,pcwalton/skia,MinimalOS-AOSP/platform_external_skia,boulzordev/android_external_skia,nfxosp/platform_external_skia,Infinitive-OS/platform_external_skia,shahrzadmn/skia,tmpvar/skia.cc,google/skia,ominux/skia,Infinitive-OS/platform_external_skia,geekboxzone/mmallow_external_skia,chenlian2015/skia_from_google,TeamExodus/external_skia,HalCanary/skia-hc,aosp-mirror/platform_external_skia,UBERMALLOW/external_skia,geekboxzone/mmallow_external_skia,MonkeyZZZZ/platform_external_skia,TeamExodus/external_skia,AOSP-YU/platform_external_skia,BrokenROM/external_skia,AOSPB/external_skia,TeamTwisted/external_skia,Hikari-no-Tenshi/android_external_skia,rubenvb/skia,Hikari-no-Tenshi/android_external_skia,google/skia,MarshedOut/android_external_skia,geekboxzone/mmallow_external_skia,samuelig/skia,jtg-gg/skia,nfxosp/platform_external_skia,shahrzadmn/skia,PAC-ROM/android_external_skia,nvoron23/skia,MonkeyZZZZ/platform_external_skia,YUPlayGodDev/platform_external_skia,samuelig/skia,shahrzadmn/skia,Jichao/skia,UBERMALLOW/external_skia,PAC-ROM/android_external_skia,aosp-mirror/platform_external_skia,samuelig/skia,nvoron23/skia,todotodoo/skia,vanish87/skia,AOSP-YU/platform_external_skia,shahrzadmn/skia,UBERMALLOW/external_skia,chenlian2015/skia_from_google,boulzordev/android_external_skia,Igalia/skia,PAC-ROM/android_external_skia,shahrzadmn/skia,AOSPB/external_skia,aosp-mirror/platform_external_skia,AOSPB/external_skia,VRToxin-AOSP/android_external_skia,spezi77/android_external_skia,VRToxin-AOSP/android_external_skia,jtg-gg/skia,UBERMALLOW/external_skia,Hikari-no-Tenshi/android_external_skia,noselhq/skia,pcwalton/skia,invisiblek/android_external_skia,invisiblek/android_external_skia,Infinitive-OS/platform_external_skia,BrokenROM/external_skia,HalCanary/skia-hc,qrealka/skia-hc,OneRom/external_skia,pcwalton/skia,tmpvar/skia.cc,YUPlayGodDev/platform_external_skia,BrokenROM/external_skia,MinimalOS-AOSP/platform_external_skia,Jichao/skia,TeamTwisted/external_skia,TeamExodus/external_skia,YUPlayGodDev/platform_external_skia,AOSPB/external_skia,nvoron23/skia,OneRom/external_skia,noselhq/skia,qrealka/skia-hc,UBERMALLOW/external_skia,noselhq/skia,amyvmiwei/skia,jtg-gg/skia,geekboxzone/mmallow_external_skia,noselhq/skia,amyvmiwei/skia,scroggo/skia,Hikari-no-Tenshi/android_external_skia,OneRom/external_skia,Hikari-no-Tenshi/android_external_skia,Jichao/skia,ominux/skia,chenli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