Make getComputedStyle's pseudoElt argument nullable again

The getComputedStyle IDL was synced with the spec in r186258:
https://codereview.chromium.org/765123002

This caused a performance regression in a Dromaeo test:
http://dromaeo.com/?jslib-style-jquery

The likely cause is that jQuery passes null for the pseudoElt argument:
https://github.com/jquery/jquery/search?q=getComputedStyle

With a non-nullable pseudoElt, null is converted to "null", which makes
a measurable difference. Make it nullable again to avoid the problem.

There's no observable difference, because only a pseudoElt beginning
with a : actually does anything.

BUG=438109

Review URL: https://codereview.chromium.org/774243003

git-svn-id: svn://svn.chromium.org/blink/trunk@186514 bbb929c8-8fbe-4397-9dbb-9b2b20218538
2 files changed
tree: b9dbfeee37250c71496888c4038eb4d80bad7655
  1. third_party/