Make timezone unittest less dependent on environment

Instead of only testing the current default timezone, test all
timezones.

Noticed this while looking into crbug.com/920094

Bug: none
Change-Id: Ida24c063cefb384037fc77c3673ff2d73ab7354f
Reviewed-on: https://chromium-review.googlesource.com/c/1407437
Reviewed-by: Jungshik Shin <jshin@chromium.org>
Commit-Queue: Evan Stade <estade@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622505}

base/i18n/timezone_unittest.cc

@@ -5,22 +5,34 @@
 #include "base/i18n/timezone.h"
 
 #include "testing/gtest/include/gtest/gtest.h"
+#include "third_party/icu/source/common/unicode/strenum.h"
+#include "third_party/icu/source/common/unicode/unistr.h"
+#include "third_party/icu/source/i18n/unicode/timezone.h"
 
 namespace base {
 namespace {
 
-TEST(TimezoneTest, CountryCodeForCurrentTimezone) {
-  std::string country_code = CountryCodeForCurrentTimezone();
-  // On some systems (such as Android or some flavors of Linux), ICU may come up
-  // empty. With https://chromium-review.googlesource.com/c/512282/ , ICU will
-  // not fail any more. See also http://bugs.icu-project.org/trac/ticket/13208 .
-  // Even with that, ICU returns '001' (world) for region-agnostic timezones
-  // such as Etc/UTC and |CountryCodeForCurrentTimezone| returns an empty
-  // string so that the next fallback can be tried by a customer.
-  // TODO(jshin): Revise this to test for actual timezones using
-  // use ScopedRestoreICUDefaultTimezone.
-  if (!country_code.empty())
-    EXPECT_EQ(2U, country_code.size()) << "country_code = " << country_code;
+TEST(TimezoneTest, CountryCodeForTimezones) {
+  std::unique_ptr<icu::StringEnumeration> timezones(
+      icu::TimeZone::createEnumeration());
+
+  UErrorCode status;
+  while (const icu::UnicodeString* timezone = timezones->snext(status)) {
+    icu::TimeZone::adoptDefault(icu::TimeZone::createTimeZone(*timezone));
+
+    std::string country_code = CountryCodeForCurrentTimezone();
+    // On some systems (such as Android or some flavors of Linux), ICU may come
+    // up empty. With https://chromium-review.googlesource.com/c/512282/ , ICU
+    // will not fail any more. See also
+    // http://bugs.icu-project.org/trac/ticket/13208 . Even with that, ICU
+    // returns '001' (world) for region-agnostic timezones such as Etc/UTC and
+    // |CountryCodeForCurrentTimezone| returns an empty string so that the next
+    // fallback can be tried by a customer.
+    if (!country_code.empty())
+      EXPECT_EQ(2U, country_code.size()) << "country_code = " << country_code;
+  }
+
+  icu::TimeZone::adoptDefault(nullptr);
 }
 
 }  // namespace