The submillisecond test was broken in at least two ways. First, the...

base/time_win_unittest.cc

Index: base/time_win_unittest.cc
===================================================================
--- base/time_win_unittest.cc	(revision 59966)
+++ base/time_win_unittest.cc	(working copy)
@@ -108,27 +108,29 @@
   }
 }
 
-// Flaky, http://crbug.com/42850.
-TEST(TimeTicks, FLAKY_SubMillisecondTimers) {
-  // Loop for a bit getting timers quickly.  We want to
-  // see at least one case where we get a new sample in
-  // less than one millisecond.
+TEST(TimeTicks, SubMillisecondTimers) {
+  // HighResNow doesn't work on some systems.  Since the product still works
+  // even if it doesn't work, it makes this entire test questionable.
+  if (!TimeTicks::IsHighResClockWorking())
+    return;
+
+  const int kRetries = 1000;
   bool saw_submillisecond_timer = false;
-  int64 min_timer = 1000;
-  TimeTicks last_time = TimeTicks::HighResNow();
+
+  // Run kRetries attempts to see a sub-millisecond timer.

[Paweł Hajdan Jr., 2010/09/22 09:35:32]

This test has still potential for flakiness. What if we tried to gather some
samples (1000? 10000?) and see if their statistical properties match
expectations (are within limits)? I think that should make the test more solid,
but I'm not really sure. What do you think?

[Mike Belshe, 2010/09/22 21:58:48]

Unfortunately, I don't think it helps.  In this case, we run 1000 samples
looking for just *one* that clocks in sub-millisecond.  If we don't get one
within 1000 tries, we give up.  I can't think of a way that statistical sampling
would work when just needing one doesn't.

   for (int index = 0; index < 1000; index++) {
-    TimeTicks now = TimeTicks::HighResNow();
-    TimeDelta delta = now - last_time;
-    if (delta.InMicroseconds() > 0 &&
-        delta.InMicroseconds() < 1000) {
-      if (min_timer > delta.InMicroseconds())
-        min_timer = delta.InMicroseconds();
+    TimeTicks last_time = TimeTicks::HighResNow();
+    TimeDelta delta;
+    // Spin until the clock changes a little

[Paweł Hajdan Jr., 2010/09/22 09:35:32]

nit: Dot at the end, and explain why.

[Mike Belshe, 2010/09/22 21:58:48]

Done.

+    do {
+      delta = TimeTicks::HighResNow() - last_time;
+    } while (delta.InMicroseconds() == 0);
+    if (delta.InMicroseconds() < 1000) {
       saw_submillisecond_timer = true;
+      break;
     }
-    last_time = now;
   }
   EXPECT_TRUE(saw_submillisecond_timer);
-  printf("Min timer is: %ldus\n", static_cast<long>(min_timer));
 }
 
 TEST(TimeTicks, TimeGetTimeCaps) {
@@ -230,4 +232,4 @@
 
   printf("average time drift in microseconds: %lld\n",
          total_drift / kIterations);
-}
+}