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

base/time_unittest.cc

Index: base/time_unittest.cc
diff --git a/base/time_unittest.cc b/base/time_unittest.cc
index 21e6f89c6d826fccd1e05cf979bd7546c49162f9..6ddf4d326ce2d2c8715fb829f186b3a56ec7a6ee 100644
--- a/base/time_unittest.cc
+++ b/base/time_unittest.cc
@@ -52,6 +52,19 @@ TEST(Time, TimeT) {
   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());