document.lastModified should consider user's local time zone

Source/core/html/forms/BaseDateAndTimeInputType.cpp

Index: Source/core/html/forms/BaseDateAndTimeInputType.cpp
diff --git a/Source/core/html/forms/BaseDateAndTimeInputType.cpp b/Source/core/html/forms/BaseDateAndTimeInputType.cpp
index 309d013f5feb1770f9ae170948a45a7d7920976b..de2238b92d0e77b9c1ac4e582dc4ec59993ed43d 100644
--- a/Source/core/html/forms/BaseDateAndTimeInputType.cpp
+++ b/Source/core/html/forms/BaseDateAndTimeInputType.cpp
@@ -90,11 +90,8 @@ String BaseDateAndTimeInputType::rangeUnderflowText(const Decimal& minimum) cons
 
 Decimal BaseDateAndTimeInputType::defaultValueForStepUp() const
 {
-    double ms = currentTimeMS();
-    double utcOffset = calculateUTCOffset();
-    double dstOffset = calculateDSTOffset(ms, utcOffset);
-    int offset = static_cast<int>((utcOffset + dstOffset) / msPerMinute);
-    return Decimal::fromDouble(ms + (offset * msPerMinute));
+    double current = convertToLocalTime(currentTimeMS());
+    return Decimal::fromDouble(current);
 }
 
 bool BaseDateAndTimeInputType::isSteppable() const