Revert "TimelinePanel: move conversion from OverviewGrid window to windowTimes to TimelineOverviewPane"

This reverts commit 100840fd03dc3dfc25d17421dcb0e5d143db0f52.

it breaks window filter

BUG=
TBR=pfeldman@chromium.org

Review URL: https://codereview.chromium.org/136003010

git-svn-id: svn://svn.chromium.org/blink/trunk@165946 bbb929c8-8fbe-4397-9dbb-9b2b20218538