Revert of git cl: Rework Changelist class for Rietveld/Gerrit use. (patchset #3 id:40001 of https://codereview.chromium.org/1830973003/ )

Reason for revert:
Speculative revert, see crbug.com/598428.

Original issue's description:
> git cl: Rework Changelist class for Rietveld/Gerrit use.
> 
> This adds pluggable codereview-specific implementations into
> Changelist class. The specific implementation is chosen at
> Changelist automatically, with Rietveld being default for
> backwards compatibility.
> 
> Gerrit implementation for Gerrit is incomplete, and will be
> added in later CLs. However, it is sufficient to ensure
> current functionality of this tool is not diminished.
> 
> Sadly, the base class isn't completely free from Rietveld
> assumptions because of presubmit_support. Apparently, PRESUBMIT
> scripts can make use of Rietveld instance for RPCs directly.
> This use doesn't make sense for Gerrit, which substitutes
> rietveld instance with a dummy object, which raises exception
> on any attribute access with a diagnostic message.
> 
> This also includes refactoring of some related code which
> (ab)used ChangeList. Overall, this CL adds a few extra call to
> git config in order to determine which codereview to use, but
> but it shouldn't have any performance impact.
> 
> 
> 
> These is a reland of these 4 CLs + a fix.
> patch from issue 1827523003 at patchset 20001 (http://crrev.com/1827523003#ps20001)
> patch from issue 1830703004 at patchset 1 (http://crrev.com/1830703004#ps1)
> patch from issue 1830923002 at patchset 60001 (http://crrev.com/1830923002#ps60001)
> patch from issue 1805193002 at patchset 380001 (http://crrev.com/1805193002#ps380001)
> 
> 
> 
> R=machenbach@chromium.org,sergiyb@chromium.org,andybons@chromium.org
> BUG=579160,597638
> 
> Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=299506

TBR=andybons@chromium.org,machenbach@chromium.org,sergiyb@chromium.org,tandrii@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=579160,597638

Review URL: https://codereview.chromium.org/1840833002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@299515 0039d316-1c4b-4281-b951-d872f2087c98