Accept time zones like GMT-8 in the legacy date parser

In the Date constructor or Date.parse, other browsers will accept time
zones like GMT-8, but before this patch, Chrome would interpret 8 as
8 minutes. This patch interprets GMT-+ a one or two digit number as hours,
not minutes.

R=adamk,jshin@chromium.org
LOG=Y
BUG=chromium:422858

Review URL: https://codereview.chromium.org/1557053002

Cr-Commit-Position: refs/heads/master@{#33100}

src/dateparser-inl.h

@@ -137,17 +137,29 @@ bool DateParser::Parse(Vector<Char> str,
       tz.SetSign(token.ascii_sign());
       // The following number may be empty.
       int n = 0;
+      int length = 0;
       if (scanner.Peek().IsNumber()) {
-        n = scanner.Next().number();
+        DateToken token = scanner.Next();
+        length = token.length();
+        n = token.number();
       }
       has_read_number = true;
 
       if (scanner.Peek().IsSymbol(':')) {
         tz.SetAbsoluteHour(n);
+        // TODO(littledan): Use minutes as part of timezone?
         tz.SetAbsoluteMinute(kNone);
-      } else {
+      } else if (length == 2 || length == 1) {
+        // Handle time zones like GMT-8
+        tz.SetAbsoluteHour(n);
+        tz.SetAbsoluteMinute(0);
+      } else if (length == 4 || length == 3) {
+        // Looks like the hhmm format
         tz.SetAbsoluteHour(n / 100);
         tz.SetAbsoluteMinute(n % 100);
+      } else {
+        // No need to accept time zones like GMT-12345
+        return false;
       }
     } else if ((token.IsAsciiSign() || token.IsSymbol(')')) &&
                has_read_number) {

test/mjsunit/regress/regress-crbug-422858.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.
+
+var date = new Date("2016/01/02 10:00 GMT-8")
+assertEquals(0, date.getMinutes());
+assertEquals(18, date.getUTCHours());
+
+date = new Date("2016/01/02 10:00 GMT-12")
+assertEquals(0, date.getMinutes());
+assertEquals(22, date.getUTCHours());
+
+date = new Date("2016/01/02 10:00 GMT-123")
+assertEquals(23, date.getMinutes());
+assertEquals(11, date.getUTCHours());
+
+date = new Date("2016/01/02 10:00 GMT-0856")
+assertEquals(56, date.getMinutes());
+assertEquals(18, date.getUTCHours());
+
+date = new Date("2016/01/02 10:00 GMT-08000")
+assertEquals(NaN, date.getMinutes());
+assertEquals(NaN, date.getUTCHours());