Revert of Exclude readonly and disabled elements from autofill form. (patchset #3 id:40001 of https://codereview.chromium.org/621503003/)

Reason for revert:
breaks requestAutocomplete

Original issue's description:
> Exclude readonly and disabled elements from autofill form.
>
> R=isherman@chromium.org
> BUG=231160
>
> Committed: https://crrev.com/cfe1912bcc70118364c9156e1e12c6c89b1a06b9
> Cr-Commit-Position: refs/heads/master@{#298436}

TBR=isherman@chromium.org,mkwst@chromium.org,ziran.sun@samsung.com
NOTREECHECKS=true
NOTRY=true
BUG=231160

Review URL: https://codereview.chromium.org/652783002

Cr-Commit-Position: refs/heads/master@{#299328}
7 files changed