fix for high resolution timer on windows.

base/time/time_win.cc

Index: base/time/time_win.cc
diff --git a/base/time/time_win.cc b/base/time/time_win.cc
index 492b54a93f126717ad0b2c339e75322bdeeb1532..3946bb17651b642c93bd3fc5b3a9ff6adb17a674 100644
--- a/base/time/time_win.cc
+++ b/base/time/time_win.cc
@@ -92,7 +92,7 @@ const int kMinTimerIntervalLowResMs = 4;
 // Track if kMinTimerIntervalHighResMs or kMinTimerIntervalLowResMs is active.
 bool g_high_res_timer_enabled = false;
 // How many times the high resolution timer has been called.
-int g_high_res_timer_count = 0;
+unsigned int g_high_res_timer_count = 0;

[jamesr, 2014/09/04 22:56:03]

uint32_t

'unsigned int' is redundant and we don't typically use just 'unsigned'

 // The lock to control access to the above two variables.
 base::LazyInstance<base::Lock>::Leaky g_high_res_lock =
     LAZY_INSTANCE_INITIALIZER;
@@ -197,10 +197,17 @@ bool Time::ActivateHighResolutionTimer(bool activating) {
   // We only do work on the transition from zero to one or one to zero so we
   // can easily undo the effect (if necessary) when EnableHighResolutionTimer is
   // called.
+  const unsigned int max = std::numeric_limits<unsigned int>::max();

[jamesr, 2014/09/04 22:56:03]

uint32_t

+
   base::AutoLock lock(g_high_res_lock.Get());
   UINT period = g_high_res_timer_enabled ? kMinTimerIntervalHighResMs
                                          : kMinTimerIntervalLowResMs;
-  int high_res_count =
+
+  // Check for overflow or underflow.
+  DCHECK((g_high_res_timer_count != 0) || activating);
+  DCHECK((g_high_res_timer_count != max) || !activating);
+
+  unsigned int high_res_count =
       activating ? ++g_high_res_timer_count : --g_high_res_timer_count;
 
   if (activating) {