Handle getMemoryBase returning NULL in WriteTask.
Handle getMemoryBase returning NULL in WriteTask.

DM::WriteTask::fData was changed from a data to a stream in
"SkData to SkStreamAsset to avoid unneeded copying"
https://skia.googlesource.com/skia/+/a4c6094177ebde18c706cbcfbd2013d0a088e0ee
However, DM::WriteTask::draw was not updated to handle this,
resulting in segfaults when trying to write out PDF files.

Review URL: https://codereview.chromium.org/627473002

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