Factor out common StepRange construction code.

Source/core/html/forms/DateTimeLocalInputType.cpp

Index: Source/core/html/forms/DateTimeLocalInputType.cpp
diff --git a/Source/core/html/forms/DateTimeLocalInputType.cpp b/Source/core/html/forms/DateTimeLocalInputType.cpp
index 9ad29fa594a5797fab7c5cdc3ae43682302e451e..32644449baaab2412f7ef2411b8712641f7d092c 100644
--- a/Source/core/html/forms/DateTimeLocalInputType.cpp
+++ b/Source/core/html/forms/DateTimeLocalInputType.cpp
@@ -86,11 +86,7 @@ StepRange DateTimeLocalInputType::createStepRange(AnyStepHandling anyStepHandlin
 {
     DEFINE_STATIC_LOCAL(const StepRange::StepDescription, stepDescription, (dateTimeLocalDefaultStep, dateTimeLocalDefaultStepBase, dateTimeLocalStepScaleFactor, StepRange::ScaledStepValueShouldBeInteger));
 
-    const Decimal stepBase = findStepBase(0);
-    const Decimal minimum = parseToNumber(element().fastGetAttribute(minAttr), Decimal::fromDouble(DateComponents::minimumDateTime()));
-    const Decimal maximum = parseToNumber(element().fastGetAttribute(maxAttr), Decimal::fromDouble(DateComponents::maximumDateTime()));
-    const Decimal step = StepRange::parseStep(anyStepHandling, stepDescription, element().fastGetAttribute(stepAttr));
-    return StepRange(stepBase, minimum, maximum, step, stepDescription);
+    return InputType::createStepRange(anyStepHandling, 0, Decimal::fromDouble(DateComponents::minimumDateTime()), Decimal::fromDouble(DateComponents::maximumDateTime()), stepDescription);
 }
 
 bool DateTimeLocalInputType::parseToDateComponentsInternal(const String& string, DateComponents* out) const