Improve form validation messages for input[type=email].

Add detailed validation messages for invalid email addresses in order to notify
what's wrong to users.

Blink passes fixed string parameters '@' and '.' to queryLocalizedString to avoid to translate them.

Also, it's ok to use WebLocalizedString names directly. We don't have any
reason to wrap each of localized strings with dedicated functions.

BUG=161733
TEST=automated.
R=keishi@chromium.org

Review URL: https://codereview.chromium.org/23904020

git-svn-id: svn://svn.chromium.org/blink/trunk@157943 bbb929c8-8fbe-4397-9dbb-9b2b20218538