Removed fields/methods related to gesture tap highlight flags.

This CL follows https://codereview.chromium.org/392783003 and
https://codereview.chromium.org/393653002.

BUG=350531

Review URL: https://codereview.chromium.org/396753002

git-svn-id: svn://svn.chromium.org/blink/trunk@178472 bbb929c8-8fbe-4397-9dbb-9b2b20218538