update fast/harness/hello.html to produce a new result.

Part of testing the CQ and tryservers handling binary patches; this tests
that we are updating PNGs properly.

TBR=leviw@chromium.org, iannucci@chromium.org
BUG=23608

Review URL: https://chromiumcodereview.appspot.com/23460034

git-svn-id: svn://svn.chromium.org/blink/trunk@157705 bbb929c8-8fbe-4397-9dbb-9b2b20218538