document.lastModified should consider user's local time zone

Source/core/dom/Document.cpp

Index: Source/core/dom/Document.cpp
diff --git a/Source/core/dom/Document.cpp b/Source/core/dom/Document.cpp
index eba7ecdfb87d0d206d3d79923ba3816eb5daec3d..22726422d40f4248084186ae665b4be1e49e48f5 100644
--- a/Source/core/dom/Document.cpp
+++ b/Source/core/dom/Document.cpp
@@ -195,6 +195,7 @@
 #include "platform/weborigin/SecurityOrigin.h"
 #include "public/platform/Platform.h"
 #include "wtf/CurrentTime.h"
+#include "wtf/DateMath.h"
 #include "wtf/HashFunctions.h"
 #include "wtf/MainThread.h"
 #include "wtf/StdLibExtras.h"
@@ -4069,6 +4070,13 @@ void Document::setDomain(const String& newDomain, ExceptionState& exceptionState
         m_frame->script().updateSecurityOrigin(securityOrigin());
 }
 
+static double convertToLocalTime(double ms)

[tkent, 2014/07/18 14:16:56]

We have this calculation at multiple places.
https://code.google.com/p/chromium/codesearch#search/&q=utcOffset%5Cs%5C%2B%5...

We should consolidate them.

[kangil_, 2014/07/21 02:34:42]

Done.

+{
+    double utcOffset = calculateUTCOffset();
+    double dstOffset = calculateDSTOffset(ms, utcOffset);
+    return (ms + utcOffset + dstOffset);
+}
+
 // http://www.whatwg.org/specs/web-apps/current-work/#dom-document-lastmodified
 String Document::lastModified() const
 {
@@ -4078,7 +4086,7 @@ String Document::lastModified() const
         if (DocumentLoader* documentLoader = loader()) {
             const AtomicString& httpLastModified = documentLoader->response().httpHeaderField("Last-Modified");
             if (!httpLastModified.isEmpty()) {
-                date.setMillisecondsSinceEpochForDateTime(parseDate(httpLastModified));
+                date.setMillisecondsSinceEpochForDateTime(convertToLocalTime(parseDate(httpLastModified)));
                 foundDate = true;
             }
         }
@@ -4087,7 +4095,7 @@ String Document::lastModified() const
     // specificiation tells us to read the last modification date from the file
     // system.
     if (!foundDate)
-        date.setMillisecondsSinceEpochForDateTime(currentTimeMS());
+        date.setMillisecondsSinceEpochForDateTime(convertToLocalTime(currentTimeMS()));
     return String::format("%02d/%02d/%04d %02d:%02d:%02d", date.month() + 1, date.monthDay(), date.fullYear(), date.hour(), date.minute(), date.second());
 }