Rename various variables and arguments to match the naming from the spec

This should make it easier to understand the code. I have also
simplified some calculations and gave some expressions their own
variables.

R=ojan@chromium.org
BUG=249551

Review URL: https://chromiumcodereview.appspot.com/18052028

git-svn-id: svn://svn.chromium.org/blink/trunk@153288 bbb929c8-8fbe-4397-9dbb-9b2b20218538
2 files changed