GTTF: Avoid assertion failures caused by clock drift.

Instead, we add a test dedicated to verifying the QPC
time drift. Otherwise the assertion is being flakily hit
in unrelated tests, which crashes the entire test binary.

With a dedicated test, we still have necessary monitoring,
but it's in one place.

TEST=base_unittests, net_unittests (stop crashing)
BUG=none
Review URL: http://codereview.chromium.org/3082014

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@54978 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 14 insertions, 11 deletions

diff --git a/base/time_win.cc b/base/time_win.cc
index e28835a..00868f6 100644
--- a/base/time_win.cc
+++ b/base/time_win.cc
@@ -331,22 +331,20 @@ class HighResNowSingleton {
   }
 
   TimeDelta Now() {
-    // Our maximum tolerance for QPC drifting.
-    const int kMaxTimeDriftMicroseconds = 60150;
-
-    if (IsUsingHighResClock()) {
-      int64 now = UnreliableNow();
-
-      // Verify that QPC does not seem to drift.
-      DCHECK_LT(abs((now - ReliableNow()) - skew_), kMaxTimeDriftMicroseconds);
-
-      return TimeDelta::FromMicroseconds(now);
-    }
+    if (IsUsingHighResClock())
+      return TimeDelta::FromMicroseconds(UnreliableNow());
 
     // Just fallback to the slower clock.
     return RolloverProtectedNow();
   }
 
+  int64 GetQPCDriftMicroseconds() {
+    if (!IsUsingHighResClock())
+      return 0;
+
+    return abs((UnreliableNow() - ReliableNow()) - skew_);
+  }
+
  private:
   // Synchronize the QPC clock with GetSystemTimeAsFileTime.
   void InitializeClock() {
@@ -398,3 +396,8 @@ TimeTicks TimeTicks::Now() {
 TimeTicks TimeTicks::HighResNow() {
   return TimeTicks() + Singleton<HighResNowSingleton>::get()->Now();
 }
+
+// static
+int64 TimeTicks::GetQPCDriftMicroseconds() {
+  return Singleton<HighResNowSingleton>::get()->GetQPCDriftMicroseconds();
+}
\ No newline at end of file