Do not compare case-insensitive for 16bit pseudo identifier
Do not lower the 16-bit pseudo identifiers, they can't match the
internal recognized pseudo names which are all ASCII.
Relevant spec information [1]:
"All CSS syntax is case-insensitive within the ASCII range (i.e.,
[a-z] and [A-Z] are equivalent), except for parts that are not
under the control of CSS."
Test taken from:
https://test.csswg.org/source/css21/syntax/case-sensitive-003.xht
Behavior matches Firefox.
[1] http://www.w3.org/TR/CSS21/syndata.html#characters
Review URL: https://codereview.chromium.org/
1135563002
git-svn-id: svn://svn.chromium.org/blink/trunk@195169 bbb929c8-8fbe-4397-9dbb-9b2b20218538