Revert of Enable VK overscroll by default. (https://codereview.chromium.org/260413002/)
Revert of Enable VK overscroll by default. (https://codereview.chromium.org/260413002/)

Reason for revert:
Speculative revert, suspecting that it breaks ash_unittests.

http://goo.gl/ZxoISj
http://goo.gl/RlD70H

Original issue's description:
> Enable VK overscroll by default.
> 
> BUG=242933
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=267115

TBR=bshe@chromium.org,kevers@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=242933

Review URL: https://codereview.chromium.org/253303003

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@267150 0039d316-1c4b-4281-b951-d872f2087c98

fujunwei/chromium-crosswalk,dednal/chromium.src,PeterWangIntel/chromium-crosswalk,chuan9/chromium-crosswalk,krieger-od/nwjs_chromium.src,markYoungH/chromium.src,dednal/chromium.src,hgl888/chromium-crosswalk,dednal/chromium.src,dushu1203/chromium.src,hgl888/chromium-crosswalk-efl,chuan9/chromium-crosswalk,M4sse/chromium.src,dednal/chromium.src,ltilve/chromium,ltilve/chromium,PeterWangIntel/chromium-crosswalk,dushu1203/chromium.src,Chilledheart/chromium,dushu1203/chromium.src,Pluto-tv/chromium-crosswalk,ltilve/chromium,krieger-od/nwjs_chromium.src,bright-sparks/chromium-spacewalk,Just-D/chromium-1,M4sse/chromium.src,krieger-od/nwjs_chromium.src,axinging/chromium-crosswalk,jaruba/chromium.src,jaruba/chromium.src,TheTypoMaster/chromium-crosswalk,M4sse/chromium.src,jaruba/chromium.src,dednal/chromium.src,ondra-novak/chromium.src,hgl888/chromium-crosswalk,ltilve/chromium,mohamed--abdel-maksoud/chromium.src,axinging/chromium-crosswalk,M4sse/chromium.src,hgl888/chromium-crosswalk-efl,krieger-od/nwjs_chromium.src,TheTypoMaster/chromium-crosswalk,hgl888/chromium-crosswalk,Pluto-tv/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,Just-D/chromium-1,Chilledheart/chromium,hgl888/chromium-crosswalk-efl,fujunwei/chromium-crosswalk,mohamed--abdel-maksoud/chromium.src,fujunwei/chromium-crosswalk,dushu1203/chromium.src,TheTypoMaster/chromium-crosswalk,ltilve/chromium,krieger-od/nwjs_chromium.src,Chilledheart/chromium,hgl888/chromium-crosswalk-efl,Pluto-tv/chromium-crosswalk,axinging/chromium-crosswalk,markYoungH/chromium.src,Fireblend/chromium-crosswalk,Chilledheart/chromium,bright-sparks/chromium-spacewalk,axinging/chromium-crosswalk,Just-D/chromium-1,axinging/chromium-crosswalk,axinging/chromium-crosswalk,chuan9/chromium-crosswalk,mohamed--abdel-maksoud/chromium.src,M4sse/chromium.src,bright-sparks/chromium-spacewalk,PeterWangIntel/chromium-crosswalk,jaruba/chromium.src,Fireblend/chromium-crosswalk,Fireblend/chromium-crosswalk,dednal/chromium.src,dushu1203/chromium.src,bright-sparks/chromium-spacewalk,Pluto-tv/chromium-crosswalk,M4sse/chromium.src,krieger-od/nwjs_chromium.src,mohamed--abdel-maksoud/chromium.src,crosswalk-project/chromium-crosswalk-efl,mohamed--abdel-maksoud/chromium.src,markYoungH/chromium.src,crosswalk-project/chromium-crosswalk-efl,littlstar/chromium.src,Jonekee/chromium.src,littlstar/chromium.src,jaruba/chromium.src,Pluto-tv/chromium-crosswalk,hgl888/chromium-crosswalk,fujunwei/chromium-crosswalk,krieger-od/nwjs_chromium.src,TheTypoMaster/chromium-crosswalk,Just-D/chromium-1,axinging/chromium-crosswalk,Jonekee/chromium.src,mohamed--abdel-maksoud/chromium.src,Jonekee/chromium.src,dushu1203/chromium.src,chuan9/chromium-crosswalk,krieger-od/nwjs_chromium.src,krieger-od/nwjs_chromium.src,ondra-novak/chromium.src,ondra-novak/chromium.src,jaruba/chromium.src,Fireblend/chromium-crosswalk,dednal/chromium.src,mohamed--abdel-maksoud/chromium.src,hgl888/chromium-crosswalk,dushu1203/chromium.src,TheTypoMaster/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,hgl888/chromium-crosswalk-efl,chuan9/chromium-crosswalk,Pluto-tv/chromium-crosswalk,hgl888/chromium-crosswalk,Fireblend/chromium-crosswalk,littlstar/chromium.src,crosswalk-project/chromium-crosswalk-efl,Pluto-tv/chromium-crosswalk,Jonekee/chromium.src,bright-sparks/chromium-spacewalk,TheTypoMaster/chromium-crosswalk,crosswalk-project/chromium-crosswalk-efl,dednal/chromium.src,Jonekee/chromium.src,bright-sparks/chromium-spacewalk,chuan9/chromium-crosswalk,littlstar/chromium.src,M4sse/chromium.src,markYoungH/chromium.src,M4sse/chromium.src,PeterWangIntel/chromium-crosswalk,dushu1203/chromium.src,PeterWangIntel/chromium-crosswalk,fujunwei/chromium-crosswalk,axinging/chromium-crosswalk,jaruba/chromium.src,mohamed--abdel-maksoud/chromium.src,hgl888/chromium-crosswalk-efl,Chilledheart/chromium,M4sse/chromium.src,mohamed--abdel-maksoud/chromium.src,dushu1203/chromium.src,Jonekee/chromium.src,ondra-novak/chromium.src,markYoungH/chromium.src,mohamed--abdel-maksoud/chromium.src,hgl888/chromium-crosswalk,Just-D/chromium-1,crosswalk-project/chromium-crosswalk-efl,TheTypoMaster/chromium-crosswalk,markYoungH/chromium.src,Just-D/chromium-1,PeterWangIntel/chromium-crosswalk,fujunwei/chromium-crosswalk,chuan9/chromium-crosswalk,mohamed--abdel-maksoud/chromium.src,markYoungH/chromium.src,chuan9/chromium-crosswalk,jaruba/chromium.src,Jonekee/chromium.src,ondra-novak/chromium.src,crosswalk-project/chromium-crosswalk-efl,crosswalk-project/chromium-crosswalk-efl,dushu1203/chromium.src,hgl888/chromium-crosswalk-efl,ondra-novak/chromium.src,jaruba/chromium.src,ondra-novak/chromium.src,Chilledheart/chromium,hgl888/chromium-crosswalk-efl,PeterWangIntel/chromium-crosswalk,markYoungH/chromium.src,TheTypoMaster/chromium-crosswalk,Jonekee/chromium.src,ltilve/chromium,Jonekee/chromium.src,hgl888/chromium-crosswalk-efl,Jonekee/chromium.src,ltilve/chromium,dednal/chromium.src,littlstar/chromium.src,Chilledheart/chromium,hgl888/chromium-crosswalk,krieger-od/nwjs_chromium.src,fujunwei/chromium-crosswalk,Fireblend/chromium-crosswalk,Chilledheart/chromium,Fireblend/chromium-crosswalk,Pluto-tv/chromium-crosswalk,fujunwei/chromium-crosswalk,markYoungH/chromium.src,Just-D/chromium-1,jaruba/chromium.src,Jonekee/chromium.src,Pluto-tv/chromium-crosswalk,M4sse/chromium.src,crosswalk-project/chromium-crosswalk-efl,dushu1203/chromium.src,hgl888/chromium-crosswalk,ondra-novak/chromium.src,ltilve/chromium,ondra-novak/chromium.src,axinging/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,dednal/chromium.src,bright-sparks/chromium-spacewalk,Fireblend/chromium-crosswalk,crosswalk-project/chromium-crosswalk-efl,markYoungH/chromium.src,Fireblend/chromium-crosswalk,littlstar/chromium.src,bright-sparks/chromium-spacewalk,dednal/chromium.src,bright-sparks/chromium-spacewalk,Just-D/chromium-1,jaruba/chromium.src,axinging/chromium-crosswalk,hgl888/chromium-crosswalk-efl,M4sse/chromium.src,krieger-od/nwjs_chromium.src,chuan9/chromium-crosswalk,fujunwei/chromium-crosswalk,axinging/chromium-crosswalk,Just-D/chromium-1,littlstar/chromium.src,Chilledheart/chromium,ltilve/chromium,littlstar/chromium.src,markYoungH/chromium.src