Derive the step base for an input element as (now) specified.

Source/core/html/forms/MonthInputType.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 90 matching lines @@
     date.setMillisecondsSinceEpochForMonth(current);
     double months = date.monthsSinceEpoch();
     ASSERT(std::isfinite(months));
     return Decimal::fromDouble(months);
 }
 
 StepRange MonthInputType::createStepRange(AnyStepHandling anyStepHandling) const
 {
     DEFINE_STATIC_LOCAL(const StepRange::StepDescription, stepDescription, (monthDefaultStep, monthDefaultStepBase, monthStepScaleFactor, StepRange::ParsedStepValueShouldBeInteger));
 
-    const Decimal stepBase = parseToNumber(element().fastGetAttribute(minAttr), Decimal::fromDouble(monthDefaultStepBase));
+    const Decimal stepBase = findStepBase(Decimal::fromDouble(monthDefaultStepBase));
     const Decimal minimum = parseToNumber(element().fastGetAttribute(minAttr), Decimal::fromDouble(DateComponents::minimumMonth()));
     const Decimal maximum = parseToNumber(element().fastGetAttribute(maxAttr), Decimal::fromDouble(DateComponents::maximumMonth()));
     const Decimal step = StepRange::parseStep(anyStepHandling, stepDescription, element().fastGetAttribute(stepAttr));
     return StepRange(stepBase, minimum, maximum, step, stepDescription);
 }
 
 Decimal MonthInputType::parseToNumber(const String& src, const Decimal& defaultValue) const
 {
     DateComponents date;
     if (!parseToDateComponents(src, &date))
@@ skipping 40 matching lines @@
     layoutParameters.placeholderForMonth = "--";
     layoutParameters.placeholderForYear = "----";
 }
 
 bool MonthInputType::isValidFormat(bool hasYear, bool hasMonth, bool hasWeek, bool hasDay, bool hasAMPM, bool hasHour, bool hasMinute, bool hasSecond) const
 {
     return hasYear && hasMonth;
 }
 #endif
 } // namespace WebCore