document.lastModified should consider user's local time zone

Source/core/html/forms/BaseDateAndTimeInputType.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 72 matching lines @@
     return locale().queryString(WebLocalizedString::ValidationRangeOverflowDateTime, localizeValue(serialize(maximum)));
 }
 
 String BaseDateAndTimeInputType::rangeUnderflowText(const Decimal& minimum) const
 {
     return locale().queryString(WebLocalizedString::ValidationRangeUnderflowDateTime, localizeValue(serialize(minimum)));
 }
 
 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));
+    return Decimal::fromDouble(convertToLocalTime(currentTimeMS()));
 }
 
 bool BaseDateAndTimeInputType::isSteppable() const
 {
     return true;
 }
 
 Decimal BaseDateAndTimeInputType::parseToNumber(const String& source, const Decimal& defaultValue) const
 {
     DateComponents date;
@@ skipping 75 matching lines @@
 {
     return element().isRequired() && value.isEmpty();
 }
 
 bool BaseDateAndTimeInputType::shouldShowFocusRingOnMouseFocus() const
 {
     return true;
 }
 
 } // namespace blink