resolvedTimezone for Etc/UTC should be UTC per Ecma 402

http://unicode.org/cldr/trac/ticket/9943 added a new separate timezone
ID (Etc/UTC) distinct from "Etc/GMT" even though their behavior is
identical. This CLDR change led v8 to violate Ecma 402 requirement that
resolvedOptions().timeZone for DateTimeFormat be "UTC" for "Etc/UTC"
, "Etc/GMT", "GMT" and "UTC".

This CL made v8 compliant to Ecma 402 again.

Bug=v8:6252
TEST=intl/date-format/timezone
Change-Id: Ibe5d3a2a09680ae00de0d73d123a389710c15af0

Change-Id: Ibe5d3a2a09680ae00de0d73d123a389710c15af0
Reviewed-on: https://chromium-review.googlesource.com/496406Reviewed-by: Daniel Ehrenberg <littledan@chromium.org>
Commit-Queue: Jungshik Shin <jshin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45114}

src/objects/intl-objects.cc

@@ -173,7 +173,13 @@ void SetResolvedDateSettings(Isolate* isolate, const icu::Locale& icu_locale,
   icu::UnicodeString canonical_time_zone;
   icu::TimeZone::getCanonicalID(time_zone, canonical_time_zone, status);
   if (U_SUCCESS(status)) {
-    if (canonical_time_zone == UNICODE_STRING_SIMPLE("Etc/GMT")) {
+    // In CLDR (http://unicode.org/cldr/trac/ticket/9943), Etc/UTC is made
+    // a separate timezone ID from Etc/GMT even though they're still the same
+    // timezone. We'd not have "Etc/GMT" here because we canonicalize it and
+    // other GMT-variants to "UTC" in intl.js and "UTC" is turned to "Etc/UTC"
+    // by ICU before getting here.
+    DCHECK(canonical_time_zone != UNICODE_STRING_SIMPLE("Etc/GMT"));
+    if (canonical_time_zone == UNICODE_STRING_SIMPLE("Etc/UTC")) {
       JSObject::SetProperty(resolved,
                             factory->NewStringFromStaticChars("timeZone"),
                             factory->NewStringFromStaticChars("UTC"), SLOPPY)

test/intl/intl.status

@@ -29,9 +29,6 @@
 [ALWAYS, {
   # TODO(jochen): The following test is flaky.
   'overrides/caching': [PASS, FAIL],
-
-  # BUG(v8:6252).
-  'date-format/timezone': [PASS, FAIL],
 }],  # ALWAYS
 
 ['variant == wasm_traps', {

test/test262/test262.status

@@ -525,10 +525,6 @@
   'intl402/NumberFormat/prototype/11.3_a': [FAIL],
   'intl402/String/prototype/localeCompare/13.1.1_7': [PASS, FAIL],
 
-  # BUG(v8:6252).
-  'intl402/DateTimeFormat/6.4_a': [FAIL],
-  'intl402/DateTimeFormat/6.4_c': [FAIL],
-
   ##################### DELIBERATE INCOMPATIBILITIES #####################
 
   # https://code.google.com/p/v8/issues/detail?id=4693