Refactoring CSS grammar
Refactoring CSS grammar

Nonfunctional change.
Introduced closing_parenthesis and error_recovery to reduce code duplication.

Extracted from https://codereview.chromium.org/14969002/

BUG=140608

Review URL: https://chromiumcodereview.appspot.com/14917019

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@149948 bbb929c8-8fbe-4397-9dbb-9b2b20218538

primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs