Unconditionally enable gesture tap highlight in blink.

This is the first in a series of CLs to remove gesture tap highlight flags. Subsequent changes for this bug will remove redundant fields & methods from chromium and blink.

BUG=350531

Review URL: https://codereview.chromium.org/392783003

git-svn-id: svn://svn.chromium.org/blink/trunk@178188 bbb929c8-8fbe-4397-9dbb-9b2b20218538