Revert of Introduce SelectionAdjuster to adjust selections between DOM tree version and composed tree version

Revert of Introduce SelectionAdjuster to adjust selections between DOM tree version and composed tree version (patchset #2 id:20001 of https://codereview.chromium.org/1630903005/ )

Reason for revert:
This patch breaks text selection in DevTools
console. Please see http://crbug.com/581800 for details.

Original issue's description:
> Introduce SelectionAdjuster to adjust selections between DOM tree version and composed tree version
> 
> This patch introduces |SelectionAdjuster| class to consolidate functions
> adjusting DOM tree version and composed tree version of selections in
> |VisibleSelection| class and |SelectionEditor| in one place to avoid having
> six parameters constructor, and rude name function |createWithoutValidation()|
> to simplify source code for improving readability.
> 
> Note: For ease of reviewing to compare changes, this patch doesn't leave
> functions in original place. Following patch moves them to
> "SelectionAdjust.{cpp,h}".
> 
> This patch is a preparation of introducing |m_hasTrailingWhitespace| into
> |VisibleSelection| class, which makes six parameters constructor to seven
> parameters constructor without this patch.
> 
> BUG=n/a
> TEST=n/a; no behavior changes
> 
> Committed: https://crrev.com/647b2143c21fade656c085f5a83426e96acbd38a
> Cr-Commit-Position: refs/heads/master@{#371697}

TBR=yoichio@chromium.org,hajimehoshi@chromium.org,tkent@chromium.org,xiaochengh@chromium.org,yosin@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=n/a

[lushnikov, 2016-01-27 20:31:05]

Created Revert of Introduce SelectionAdjuster to adjust selections between DOM
tree version and composed tree version

[lushnikov, 2016-01-27 20:32:36]

The CQ bit was unchecked by lushnikov@chromium.org