Reland http://codereview.chromium.org/4139008, with a different

base/time_unittest.cc

 // Copyright (c) 2006-2008 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 <time.h>
 
 #include "base/platform_thread.h"
 #include "base/time.h"
 #include "build/build_config.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ skipping 34 matching lines @@
   EXPECT_EQ(now_t_1, now_t_2);
 
   EXPECT_EQ(10, Time().FromTimeT(10).ToTimeT());
   EXPECT_EQ(10.0, Time().FromTimeT(10).ToDoubleT());
 
   // Conversions of 0 should stay 0.
   EXPECT_EQ(0, Time().ToTimeT());
   EXPECT_EQ(0, Time::FromTimeT(0).ToInternalValue());
 }
 
+TEST(Time, FromExplodedWithMilliseconds) {
+  // Some platform implementations of FromExploded are liable to drop
+  // milliseconds if we aren't careful.
+  Time now = Time::NowFromSystemTime();
+  Time::Exploded exploded1 = {0};
+  now.UTCExplode(&exploded1);
+  exploded1.millisecond = 500;
+  Time time = Time::FromUTCExploded(exploded1);
+  Time::Exploded exploded2 = {0};
+  time.UTCExplode(&exploded2);
+  EXPECT_EQ(exploded1.millisecond, exploded2.millisecond);
+}
+
 TEST(Time, ZeroIsSymmetric) {
   Time zero_time(Time::FromTimeT(0));
   EXPECT_EQ(0, zero_time.ToTimeT());
 
   EXPECT_EQ(0.0, zero_time.ToDoubleT());
 }
 
 TEST(Time, LocalExplode) {
   Time a = Time::Now();
   Time::Exploded exploded;
@@ skipping 142 matching lines @@
   exploded.minute = 0;
   exploded.second = 0;
   exploded.millisecond = 0;
   Time t = Time::FromUTCExploded(exploded);
   // Unix 1970 epoch.
   EXPECT_EQ(GG_INT64_C(11644473600000000), t.ToInternalValue());
 
   // We can't test 1601 epoch, since the system time functions on Linux
   // only compute years starting from 1900.
 }