Invalidation set features recognized left of adjacent.

Only recognize features (foundIdent) up until we see a relation different
from SubSelector.

After we allowed selectors with adjacent combinators to use invalidation
sets, we started to acknowledge id/class/attribute to the left of adjacent
combinators as features of the rightmost compound selector because we only
looked for descendant type of selectors.

For instance, the class 'b' below were recognized as an invalidation set
feature in this selector: ".a .b + *".

R=esprehn@chromium.org,chrishtr@chromium.org
BUG=391244,391193

Review URL: https://codereview.chromium.org/365063005

git-svn-id: svn://svn.chromium.org/blink/trunk@180500 bbb929c8-8fbe-4397-9dbb-9b2b20218538