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

Source/core/html/forms/WeekInputType.cpp

Index: Source/core/html/forms/WeekInputType.cpp
diff --git a/Source/core/html/forms/WeekInputType.cpp b/Source/core/html/forms/WeekInputType.cpp
index d164ff22f4cc445d6a09c757a9069ec8c925f8f8..6b94f9ecdcc1c02f96df340bdbcca30a37192449 100644
--- a/Source/core/html/forms/WeekInputType.cpp
+++ b/Source/core/html/forms/WeekInputType.cpp
@@ -72,9 +72,9 @@ StepRange WeekInputType::createStepRange(AnyStepHandling anyStepHandling) const
 {
     DEFINE_STATIC_LOCAL(const StepRange::StepDescription, stepDescription, (weekDefaultStep, weekDefaultStepBase, weekStepScaleFactor, StepRange::ParsedStepValueShouldBeInteger));
 
-    const Decimal stepBase = parseToNumber(element().fastGetAttribute(minAttr), weekDefaultStepBase);
-    const Decimal minimum = parseToNumber(element().fastGetAttribute(minAttr), Decimal::fromDouble(DateComponents::minimumWeek()));
-    const Decimal maximum = parseToNumber(element().fastGetAttribute(maxAttr), Decimal::fromDouble(DateComponents::maximumWeek()));
+    const Decimal stepBase = parseToNumber(element().fastGetAttribute(minAttr), element().fastGetAttribute(valueAttr), weekDefaultStepBase);
+    const Decimal minimum = parseToNumber(element().fastGetAttribute(minAttr), String(), Decimal::fromDouble(DateComponents::minimumWeek()));
+    const Decimal maximum = parseToNumber(element().fastGetAttribute(maxAttr), String(), Decimal::fromDouble(DateComponents::maximumWeek()));
     const Decimal step = StepRange::parseStep(anyStepHandling, stepDescription, element().fastGetAttribute(stepAttr));
     return StepRange(stepBase, minimum, maximum, step, stepDescription);
 }