Add source-data sharding to DM.
Add source-data sharding to DM.

E.g.  out/Debug/dm --shards 4 --shard 1

This shards all inputs, GMs, SKPs, tests, etc.

BUG=skia:

Review URL: https://codereview.chromium.org/1109813002

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