Revert 281908 "Revert of Remove disable-app-list-voice-search fl..."

Revert 281908 "Revert of Remove disable-app-list-voice-search fl..."

Revert reason:
- the change seems okay, the compile error is caused because
  the builder doesn't recomile about_flags. Clobber might fix the
  issue.
- this should be reverted again if it still causes the error
  after clobber.

> Revert of Remove disable-app-list-voice-search flag. (https://codereview.chromium.org/353793003/)
>
> Reason for revert:
> Caused compile error on Blink GPU Mac Builder:
> http://build.chromium.org/p/chromium.webkit/builders/GPU%20Mac%20Builder
>
> Original issue's description:
> > Remove disable-app-list-voice-search flag.
> >
> > BUG=367341
> > R=xiyuan@chromium.org
> > TEST=compile
> >
> > Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=281904
>
> TBR=xiyuan@chromium.org,mukai@chromium.org
> NOTREECHECKS=true
> NOTRY=true
> BUG=367341
>
> Review URL: https://codereview.chromium.org/379673003

TBR=yutak@chromium.org

Review URL: https://codereview.chromium.org/374293003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@281923 0039d316-1c4b-4281-b951-d872f2087c98