[Windows] One TimeTicks clock: efficient/reliable high-res, with low-res fallback.

base/time/time_unittest.cc

Index: base/time/time_unittest.cc
diff --git a/base/time/time_unittest.cc b/base/time/time_unittest.cc
index 16d6fe9c3a2918f19d109318f8af605845d3259a..fc07d25df3ce9d833914067ab52922dd1cdf2f51 100644
--- a/base/time/time_unittest.cc
+++ b/base/time/time_unittest.cc
@@ -6,7 +6,9 @@
 
 #include <time.h>
 
+#include <limits>
 #include <string>
+#include <type_traits>
 
 #include "base/compiler_specific.h"
 #include "base/logging.h"
@@ -642,12 +644,10 @@ TEST(TimeTicks, Deltas) {
 }
 
 static void HighResClockTest(TimeTicks (*GetTicks)()) {
-#if defined(OS_WIN)
   // 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())
+  if (!TimeTicks::IsHighResolution())
     return;
-#endif
 
   // Why do we loop here?
   // We're trying to measure that intervals increment in a VERY small amount
@@ -792,6 +792,21 @@ std::string AnyToString(Any any) {
   return oss.str();
 }
 
+// Paranoia test: Since std::abs(int64) is new to C++11, make sure incomplete
+// toolchains don't silently pull in an alternate overload when the needed
+// function is missing.
+TEST(TimeDelta, ParanoidAboutAbsFunction) {

[brianderson, 2015/01/07 00:53:44]

Do you plan to remove this test before landing?

[miu, 2015/01/07 05:22:45]

The trybots on PS1 forced me to change tactics.  So, this test was somewhat
rewritten to confirm my inlined abs() implementation.

+  int64 max_int64_minus_one = std::numeric_limits<int64>::max() - 1;
+  int64 min_int64_plus_two = std::numeric_limits<int64>::min() + 2;
+  static_assert(std::is_same<decltype(max_int64_minus_one),
+                             decltype(std::abs(max_int64_minus_one))>::value,
+                "compiler is choosing incorrect std::abs() overload");
+  EXPECT_EQ(TimeDelta::FromMicroseconds(max_int64_minus_one),
+            TimeDelta::FromMicroseconds(max_int64_minus_one).magnitude());
+  EXPECT_EQ(TimeDelta::FromMicroseconds(max_int64_minus_one),
+            TimeDelta::FromMicroseconds(min_int64_plus_two).magnitude());
+}
+
 TEST(TimeDeltaLogging, DCheckEqCompiles) {
   DCHECK_EQ(TimeDelta(), TimeDelta());
 }