Timeline: remove recordingInProgress check because it is not necessary.

The overlay that would regress performance of the operations with ui
has been disabled on backend.

BUG=
R=caseq@chromium.org

Review URL: https://codereview.chromium.org/115973006

git-svn-id: svn://svn.chromium.org/blink/trunk@164295 bbb929c8-8fbe-4397-9dbb-9b2b20218538