[SVG] Handle animation freeze when 'repeatDur' is not a multiple of 'dur'

This logic originally existed in WebKit as 'if (fmod(repeatingDuration.value(), simpleDuration.value() == 0.))'.
It was supposed to read `if (fmod(...) == 0)`, but the == slipped into the fmod call and unfortunately got removed later as it looked meaningless.
This logic is meant for handling the scenario where 'repeatingDuration' is not a multiple of 'simpleDuration'.
Modified this logic in a proper way.

R=pdr@chromium.org, schenney@chromium.org, dschulze@chromium.org
BUG=262917

Review URL: https://chromiumcodereview.appspot.com/19946002

git-svn-id: svn://svn.chromium.org/blink/trunk@154777 bbb929c8-8fbe-4397-9dbb-9b2b20218538