DevTools: loading timeline pretends it is recording w/ 0 events collected.

When loading timeline data from file the progress pane message is set to "Loading from file..."

BUG=426123
R=loislo@chromium.org

Review URL: https://codereview.chromium.org/705273002

git-svn-id: svn://svn.chromium.org/blink/trunk@184980 bbb929c8-8fbe-4397-9dbb-9b2b20218538