Timeline: extract TimelineView.js from TimelinePanel.js

This patch has  no business logic changes.

BUG=
R=caseq@chromium.org, vsevik@chromium.org

Review URL: https://codereview.chromium.org/115093004

git-svn-id: svn://svn.chromium.org/blink/trunk@164298 bbb929c8-8fbe-4397-9dbb-9b2b20218538