Upgrade stepUp()/stepDown() implementation to match spec.

Source/core/html/forms/DateInputType.cpp

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 54 matching lines @@
 
 const AtomicString& DateInputType::formControlType() const
 {
     return InputTypeNames::date;
 }
 
 StepRange DateInputType::createStepRange(AnyStepHandling anyStepHandling) const
 {
     DEFINE_STATIC_LOCAL(const StepRange::StepDescription, stepDescription, (dateDefaultStep, dateDefaultStepBase, dateStepScaleFactor, StepRange::ParsedStepValueShouldBeInteger));
 
-    return InputType::createStepRange(anyStepHandling, 0, Decimal::fromDouble(DateComponents::minimumDate()), Decimal::fromDouble(DateComponents::maximumDate()), stepDescription);
+    return InputType::createStepRange(anyStepHandling, dateDefaultStepBase, Decimal::fromDouble(DateComponents::minimumDate()), Decimal::fromDouble(DateComponents::maximumDate()), stepDescription);
 }
 
 bool DateInputType::parseToDateComponentsInternal(const String& string, DateComponents* out) const
 {
     ASSERT(out);
     unsigned end;
     return out->parseDate(string, 0, end) && end == string.length();
 }
 
 bool DateInputType::setMillisecondToDateComponents(double value, DateComponents* date) const
@@ skipping 29 matching lines @@
     layoutParameters.placeholderForYear = locale().queryString(WebLocalizedString::PlaceholderForYearField);
 }
 
 bool DateInputType::isValidFormat(bool hasYear, bool hasMonth, bool hasWeek, bool hasDay, bool hasAMPM, bool hasHour, bool hasMinute, bool hasSecond) const
 {
     return hasYear && hasMonth && hasDay;
 }
 #endif
 
 } // namespace WebCore