[FastTextAutosizer] Refactor {isWider,isNarrower}Descendant into one fn

Two codes for the price of one codes:
isWiderDescendant + isNarrowerDescendant -> isWiderOrNarrowerDescendant
I have recently learned pay is not depend on lines of code. This change
make code squeaky clean and re-use common logic to make benefit
glorious fast text autosizer.

BUG=302005

Review URL: https://codereview.chromium.org/176503002

git-svn-id: svn://svn.chromium.org/blink/trunk@167723 bbb929c8-8fbe-4397-9dbb-9b2b20218538