Fixed invalid input values in lighting filters

A few values have specified ranges in the W3 spec:
- specularExponent = Range 1.0 to 128.0
- specularConstant = any non-negative number
- diffuseConstant = any non-negative number

I made sure these restrictions were respected. A few layout tests using out of range specularExponent values will have to be rebaselined.

BUG=351807

Review URL: https://codereview.chromium.org/196973006

git-svn-id: svn://svn.chromium.org/blink/trunk@169130 bbb929c8-8fbe-4397-9dbb-9b2b20218538