Refactoring: Do not do both of UI-specific things and others in one InputType function.

InputType::handleFocusEvent was used for multiple-fields focus handling in
BaseMultipleFieldsDateAndTimeInputType and secure text input handling in
PasswordInputType. The former is for a specific UI, and the latter is an
essential behavior of input[type=password]. We'd like to separate UI-specific
functions from others. So we introduce InputType::enableSecureTextInput.

Also we introduce InputType::disableSecureTextInput and
sanitizeValueInResponseToMinOrMaxAttributeChange for the same reason.

This is a preparation to support author shadow DOM for INPUT element.

BUG=274205

Review URL: https://chromiumcodereview.appspot.com/23286005

git-svn-id: svn://svn.chromium.org/blink/trunk@156464 bbb929c8-8fbe-4397-9dbb-9b2b20218538