timezone match code - consider canonical id as well

chromeos/settings/timezone_settings_helper.cc

Index: chromeos/settings/timezone_settings_helper.cc
diff --git a/chromeos/settings/timezone_settings_helper.cc b/chromeos/settings/timezone_settings_helper.cc
new file mode 100644
index 0000000000000000000000000000000000000000..781f774d8b1f84d856c0caae492752409244f341
--- /dev/null
+++ b/chromeos/settings/timezone_settings_helper.cc
@@ -0,0 +1,45 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chromeos/settings/timezone_settings_helper.h"
+
+#include "base/logging.h"
+#include "chromeos/chromeos_export.h"
+
+namespace chromeos {
+namespace system {
+
+CHROMEOS_EXPORT const icu::TimeZone* GetKnownTimezoneOrNull(
+    const icu::TimeZone& timezone,
+    const std::vector<icu::TimeZone*>& timezone_list) {
+  const icu::TimeZone* known_timezone = NULL;
+  icu::UnicodeString id, canonical_id;
+  timezone.getID(id);
+  UErrorCode status = U_ZERO_ERROR;
+  icu::TimeZone::getCanonicalID(id, canonical_id, status);
+  DCHECK(U_SUCCESS(status));
+  for (const auto* entry : timezone_list) {
+    if (*entry == timezone)
+      return entry;
+    // Compare the canonical IDs as well.
+    // For instance, Asia/Ulan_Bator -> Asia/Ulaanbaatar or
+    // Canada/Pacific -> America/Vancouver
+    icu::UnicodeString entry_id, entry_canonical_id;
+    entry->getID(entry_id);
+    icu::TimeZone::getCanonicalID(entry_id, entry_canonical_id, status);
+    DCHECK(U_SUCCESS(status));
+    if (entry_canonical_id == canonical_id)
+      return entry;
+    // Last resort: If no match is found, the last timezone in the list
+    // with matching rules will be returned.
+    if (entry->hasSameRules(timezone))
+      known_timezone = entry;
+  }
+
+  // May return NULL if we did not find a matching timezone in our list.
+  return known_timezone;
+}
+
+}  // namespace system
+}  // namespace chromeos