Merge to XFA: Fix JS seconds since epoch to date conversions.

fpdfsdk/src/javascript/JS_Value.cpp

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "JS_Value.h"
 
 #include <time.h>
 #include <cmath>
@@ skipping 631 matching lines @@
   return (year % 4 == 0) && ((year % 100 != 0) || (year % 400 != 0));
 }
 
 int _DayFromYear(int y) {
   return (int)(365 * (y - 1970.0) + FXSYS_floor((y - 1969.0) / 4) -
                FXSYS_floor((y - 1901.0) / 100) +
                FXSYS_floor((y - 1601.0) / 400));
 }
 
 double _TimeFromYear(int y) {
-  return ((double)86400000) * _DayFromYear(y);
+  return 86400000.0 * _DayFromYear(y);
 }
 
 double _TimeFromYearMonth(int y, int m) {
   static int daysMonth[12] = {
       0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334};
   static int leapDaysMonth[12] = {
       0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335};
   int* pMonth = daysMonth;
   if (_isLeapYear(y))
     pMonth = leapDaysMonth;
   return _TimeFromYear(y) + ((double)pMonth[m]) * 86400000;
 }
 
 int _Day(double t) {
   return (int)FXSYS_floor(t / 86400000);
 }
 
 int _YearFromTime(double t) {
   // estimate the time.
-  int y = 1970 + (int)(t / (365.0 * 86400000));
+  int y = 1970 + static_cast<int>(t / (365.2425 * 86400000));
   if (_TimeFromYear(y) <= t) {
     while (_TimeFromYear(y + 1) <= t)
       y++;
   } else
-    while (_TimeFromYear(y - 1) > t)
+    while (_TimeFromYear(y) > t)
       y--;
   return y;
 }
 
 int _DayWithinYear(double t) {
   int year = _YearFromTime(t);
   int day = _Day(t);
   return day - _DayFromYear(year);
 }
 
@@ skipping 174 matching lines @@
   return day * 86400000 + time;
 }
 
 bool JS_PortIsNan(double d) {
   return d != d;
 }
 
 double JS_LocalTime(double d) {
   return JS_GetDateTime() + _getDaylightSavingTA(d);
 }