Revert of Revert of [MemSherrif] Uninitialized Read (patchset #2 id:40001 of https://codereview.chromium.org/986763002/)
Revert of Revert of [MemSherrif] Uninitialized Read (patchset #2 id:40001 of https://codereview.chromium.org/986763002/)

Reason for revert:
DrMemory bots still hit the bug: http://build.chromium.org/p/chromium.memory.fyi/builders/Windows%20Content%20Browser%20%28DrMemory%20full%29%20%286%29/builds/3752

Original issue's description:
> Revert of [MemSherrif] Uninitialized Read (patchset #1 id:1 of https://codereview.chromium.org/969073002/)
>
> Reason for revert:
> Uninitialized read should now be fixed (and there is a test). Should this revert break the DrMemory bots, this revert should be reverted.
>
> Original issue's description:
> > [MemSherrif] Uninitialized Read
> >
> > BUG=463204
> > TBR=reed@chromium.org, thestig@chromium.org
> >
> > Committed: https://crrev.com/94d1b7498d7b5c4fc25e3337be117f8c9ef1dbf2
> > Cr-Commit-Position: refs/heads/master@{#318760}
>
> TBR=thestig@chromium.org,groby@chromium.org
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=463204
>
> Committed: https://crrev.com/82417f64ce69c98a93f82f59e6adda1c9c2e510c
> Cr-Commit-Position: refs/heads/master@{#319503}

TBR=groby@chromium.org,bungeman@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=463204

Review URL: https://codereview.chromium.org/984073007

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#319553}

axinging/chromium-crosswalk,Chilledheart/chromium,chuan9/chromium-crosswalk,Pluto-tv/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,Fireblend/chromium-crosswalk,ltilve/chromium,fujunwei/chromium-crosswalk,axinging/chromium-crosswalk,Chilledheart/chromium,Pluto-tv/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,fujunwei/chromium-crosswalk,fujunwei/chromium-crosswalk,Just-D/chromium-1,Just-D/chromium-1,Just-D/chromium-1,axinging/chromium-crosswalk,axinging/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,chuan9/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,Just-D/chromium-1,PeterWangIntel/chromium-crosswalk,fujunwei/chromium-crosswalk,Chilledheart/chromium,Pluto-tv/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,Fireblend/chromium-crosswalk,chuan9/chromium-crosswalk,Pluto-tv/chromium-crosswalk,Fireblend/chromium-crosswalk,axinging/chromium-crosswalk,fujunwei/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,hgl888/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,axinging/chromium-crosswalk,Pluto-tv/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,Just-D/chromium-1,hgl888/chromium-crosswalk,axinging/chromium-crosswalk,chuan9/chromium-crosswalk,Fireblend/chromium-crosswalk,Pluto-tv/chromium-crosswalk,Fireblend/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,ltilve/chromium,Just-D/chromium-1,chuan9/chromium-crosswalk,ltilve/chromium,ltilve/chromium,ltilve/chromium,Chilledheart/chromium,hgl888/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,ltilve/chromium,fujunwei/chromium-crosswalk,chuan9/chromium-crosswalk,Chilledheart/chromium,Pluto-tv/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,Pluto-tv/chromium-crosswalk,Fireblend/chromium-crosswalk,axinging/chromium-crosswalk,Just-D/chromium-1,fujunwei/chromium-crosswalk,axinging/chromium-crosswalk,ltilve/chromium,TheTypoMaster/chromium-crosswalk,ltilve/chromium,Fireblend/chromium-crosswalk,Fireblend/chromium-crosswalk,hgl888/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,axinging/chromium-crosswalk,Chilledheart/chromium,chuan9/chromium-crosswalk,chuan9/chromium-crosswalk,chuan9/chromium-crosswalk,hgl888/chromium-crosswalk,hgl888/chromium-crosswalk,hgl888/chromium-crosswalk,Fireblend/chromium-crosswalk,Just-D/chromium-1,hgl888/chromium-crosswalk,Chilledheart/chromium,Chilledheart/chromium,Pluto-tv/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,hgl888/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,fujunwei/chromium-crosswalk,Just-D/chromium-1,PeterWangIntel/chromium-crosswalk,ltilve/chromium,fujunwei/chromium-crosswalk,axinging/chromium-crosswalk,Chilledheart/chromium