update flakiness dashboard to point to google cloud storage for results.

This patch depends on crbug.com/261742 being fixed first (or at least,
we shouldn't make an app live that contains this change until then).

R=ojan@chromium.org
BUG=261753

Review URL: https://codereview.chromium.org/19460011

git-svn-id: svn://svn.chromium.org/blink/trunk@157250 bbb929c8-8fbe-4397-9dbb-9b2b20218538