Revert "Keep looking for allowed punctuation when punctuation that precedes the first letter is already found."

We need to revert this commit because all browsers including IE10 follow the CSS specifications
below:

Punctuation (i.e, characters defined in Unicode [UNICODE] in the "open" (Ps), "close" (Pe),
"initial" (Pi). "final" (Pf) and "other" (Po) punctuation classes), that precedes or follows
the first letter should be included.

http://www.w3.org/TR/CSS2/selector.html#first-letter
http://www.w3.org/TR/css3-selectors/#first-letter

Including @ as punctuation seems to be strange as the bug report(61724) said, but we have
to follow the CSS specifications like other browsers.

This reverts commit 2390d478685cc9e8b1ec0ec29d4d0afa96222dd6.

Conflicts:
	LayoutTests/TestExpectations

BUG=61724

Review URL: https://codereview.chromium.org/115953004

git-svn-id: svn://svn.chromium.org/blink/trunk@164167 bbb929c8-8fbe-4397-9dbb-9b2b20218538