Add doc on SkCanvas::drawImage*() methods
Add doc on SkCanvas::drawImage*() methods

BUG=skia:2947
R=junov@chromium.org, reed@google.com

Author: piotaixr@chromium.org

Review URL: https://codereview.chromium.org/595043002

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