Fix 'illegal access' in Date constructor edge case

In a rare edge case, a difference in checks between C++ and
JavaScript lead to an 'illegal access' being thrown by the Date
constructor. This patch harmonizes the checks from both sides.
It's possible that slightly larger dates could be permitted,
as the ECMAScript 2015 specification indicates that +287396-10-12
would be a permissible date in the note in
http://tc39.github.io/ecma262/#sec-extended-years
This patch does not revisit the limit, only clears up the
inconsistency.

BUG=v8:4640
R=cbruni
LOG=Y

Review URL: https://codereview.chromium.org/1545883003

Cr-Commit-Position: refs/heads/master@{#33068}

src/date.h

@@ -18,6 +18,7 @@ class DateCache {
   static const int kMsPerMin = 60 * 1000;
   static const int kSecPerDay = 24 * 60 * 60;
   static const int64_t kMsPerDay = kSecPerDay * 1000;
+  static const int64_t kMsPerMonth = kMsPerDay * 30;
 
   // The largest time that can be passed to OS date-time library functions.
   static const int kMaxEpochTimeInSec = kMaxInt;
@@ -30,8 +31,7 @@ class DateCache {
 
   // Conservative upper bound on time that can be stored in JSDate
   // before UTC conversion.
-  static const int64_t kMaxTimeBeforeUTCInMs =
-      kMaxTimeInMs + 10 * kMsPerDay;
+  static const int64_t kMaxTimeBeforeUTCInMs = kMaxTimeInMs + kMsPerMonth;
 
   // Sentinel that denotes an invalid local offset.
   static const int kInvalidLocalOffsetInMs = kMaxInt;

test/mjsunit/regress/regress-4640.js

+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Some surrounding cases which already worked, for good measure
+assertTrue(new Date('275760-10-14') == 'Invalid Date');
+assertTrue(new Date('275760-09-23') == 'Invalid Date');
+assertTrue(new Date('+275760-09-24') == 'Invalid Date');
+assertTrue(new Date('+275760-10-13') == 'Invalid Date');
+
+// The following cases used to throw "illegal access"
+assertTrue(new Date('275760-09-24') == 'Invalid Date');
+assertTrue(new Date('275760-10-13') == 'Invalid Date');
+assertTrue(new Date('+275760-10-13 ') == 'Invalid Date');
+
+// However, dates within the range or valid
+assertTrue(new Date('100000-10-13') != 'Invalid Date');
+assertTrue(new Date('+100000-10-13') != 'Invalid Date');
+assertTrue(new Date('+100000-10-13 ') != 'Invalid Date');