Remove unused functions in HTMLInputElement, InputTypes, and StepRange.

Remove:
 - HTMLInputElement::canHaveSelection()
 - HTMLInputElement::accept()
 - HTMLInputElement::visibleValue()
 - HTMLInputElement::isColorControl()
 - HTMLInputElement::isSubmitButton()
 - HTMLInputElement::icon() declaration
 - HTMLInputElement::supportsMaxLength()
 - InputType::parseToDateComponents()
 - InputType::shouldResetOnDocumentActivation()
 - InputType::isSubmitButton()
 - PasswordInputType::shouldResetOnDocumentActivation()
 - StepRange::stepScaleFactor()
 - SubmitInputType::isSubmitButton()

Remove InputType::parseToDateComponents(), and make
BaseDateAndTimeInputType::parseToDateComponents() non-virtual.

BUG=

Review URL: https://codereview.chromium.org/117893003

git-svn-id: svn://svn.chromium.org/blink/trunk@164066 bbb929c8-8fbe-4397-9dbb-9b2b20218538