SkTime: return timezone information

src/core/SkTime.cpp

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkString.h"
+#include "SkTime.h"
+
+void SkTime::DateTime::toISO8601(SkString* dst) const {
+    if (dst) {
+        int timeZoneMinutes = SkToInt(fTimeZoneMinutes);
+        char timezoneSign = timeZoneMinutes >= 0 ? '+' : '-';
+        int timeZoneHours = abs(timeZoneMinutes) / 60;
+        timeZoneMinutes = abs(timeZoneMinutes) % 60;
+        dst->printf("%04u-%02u-%02uT%02u:%02u:%02u%c%02d:%02d",
+                    static_cast<unsigned>(fYear), static_cast<unsigned>(fMonth),
+                    static_cast<unsigned>(fDay), static_cast<unsigned>(fHour),
+                    static_cast<unsigned>(fMinute),
+                    static_cast<unsigned>(fSecond), timezoneSign, timeZoneHours,
+                    timeZoneMinutes);
+    }
+}