revert r171206: "Add transaction detail params to requestAutocomplete()."

Since rAc was adopted into the standard, we revisited this and decided
to do it a different way. This "revert" does keep the minor change
about removing the extra param to
WebAutofillClient::didRequestAutocomplete.

BUG=354897

Review URL: https://codereview.chromium.org/293853002

git-svn-id: svn://svn.chromium.org/blink/trunk@175608 bbb929c8-8fbe-4397-9dbb-9b2b20218538