[Night Light] CL4: Automatic schedule backend.

ash/system/night_light/time_of_day.cc

Index: ash/system/night_light/time_of_day.cc
diff --git a/ash/system/night_light/time_of_day.cc b/ash/system/night_light/time_of_day.cc
new file mode 100644
index 0000000000000000000000000000000000000000..049750a849e15df28636494d82eaca3457c29726
--- /dev/null
+++ b/ash/system/night_light/time_of_day.cc
@@ -0,0 +1,55 @@
+// Copyright 2017 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 "ash/system/night_light/time_of_day.h"
+
+#include "base/i18n/time_formatting.h"
+#include "base/strings/utf_string_conversions.h"
+
+namespace ash {
+
+namespace {
+
+constexpr int kMaxOffsetMinutes = 24 * 60;
+
+}  // namespace
+
+TimeOfDay::TimeOfDay(int offset_minutes)
+    : offset_minutes_from_zero_hour_(
+          offset_minutes == kMaxOffsetMinutes ? 0 : offset_minutes) {
+  DCHECK_LE(offset_minutes_from_zero_hour_, kMaxOffsetMinutes);
+}
+
+// static
+TimeOfDay TimeOfDay::FromTime(const base::Time& time) {
+  base::Time::Exploded exploded;
+  time.LocalExplode(&exploded);
+  return TimeOfDay(exploded.hour * 60 + exploded.minute);
+}
+
+bool TimeOfDay::operator==(const TimeOfDay& rhs) const {
+  return offset_minutes_from_zero_hour_ == rhs.offset_minutes_from_zero_hour_;
+}
+
+base::Time TimeOfDay::ToTimeToday() const {
+  base::Time::Exploded now;
+  base::Time::Now().LocalExplode(&now);
+  now.hour = (offset_minutes_from_zero_hour_ / 60) % 24;
+  now.minute = offset_minutes_from_zero_hour_ % 60;
+  now.second = 0;
+  now.millisecond = 0;
+  base::Time result;
+  if (base::Time::FromLocalExploded(now, &result))
+    return result;
+
+  // This function must not fail.
+  NOTREACHED();

[James Cook, 2017/05/24 15:42:46]

super-nit: I still think FromLocalExploded() can fail in pathological daylight
savings time transitions (specifically, for TimeOfDay == 2:30 AM on the "spring
forward" DST transition that goes from 01:59 to 03:00 instantaneously). I would
remove the NOTREACHED() and comment that DST is weird and it's OK to have a
funky time in that rare case.

[afakhry, 2017/05/24 16:25:35]

Done.

+  return base::Time();
+}
+
+std::string TimeOfDay::ToString() const {
+  return base::UTF16ToUTF8(base::TimeFormatTimeOfDay(ToTimeToday()));
+}
+
+}  // namespace ash