document.lastModified should consider user's local time zone

Source/core/html/shadow/DateTimeFieldElements.cpp

Index: Source/core/html/shadow/DateTimeFieldElements.cpp
diff --git a/Source/core/html/shadow/DateTimeFieldElements.cpp b/Source/core/html/shadow/DateTimeFieldElements.cpp
index 2a324e2610fa03cac4912b437e533d6cbc736d21..14e72f1084298cf233ea718b63c4fc7fcf10828e 100644
--- a/Source/core/html/shadow/DateTimeFieldElements.cpp
+++ b/Source/core/html/shadow/DateTimeFieldElements.cpp
@@ -589,12 +589,7 @@ PassRefPtrWillBeRawPtr<DateTimeYearFieldElement> DateTimeYearFieldElement::creat
 
 static int currentFullYear()
 {
-    double current = currentTimeMS();
-    double utcOffset = calculateUTCOffset();
-    double dstOffset = calculateDSTOffset(current, utcOffset);
-    int offset = static_cast<int>((utcOffset + dstOffset) / msPerMinute);
-    current += offset * msPerMinute;
-
+    double current = convertToLocalTime(currentTimeMS());
     DateComponents date;
     date.setMillisecondsSinceEpochForMonth(current);
     return date.fullYear();