Revert of Adding split view divider widget. (patchset #15 id:280001 of https://codere...

Revert of Adding split view divider widget. (patchset #15 id:280001 of https://codereview.chromium.org/545393002/)

Reason for revert:
DragHandleTest.ScrollTest is failing on the bots: http://build.chromium.org/p/chromium.chromiumos/builders/Linux%20ChromiumOS%20Tests%20%28dbg%29%283%29/builds/36880

Original issue's description:
> Adding split view divider widget.
>
> Adding split view divider widget which could be dragged to exit the split view.
>
> BUG=403207,408691
>
> Committed: https://crrev.com/b47c16517f0882cbabf8c9aa9ce66711f026fd5b
> Cr-Commit-Position: refs/heads/master@{#296351}

TBR=mukai@chromium.org,oshima@chromium.org,sadrul@chromium.org,tdanderson@chromium.org,pkotwicz@chromium.org,mfomitchev@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=403207,408691

Review URL: https://codereview.chromium.org/602603003

Cr-Commit-Position: refs/heads/master@{#296433}