Use DwmGetCompositionTimingInfo to get vsync info on Windows

base/time_win.cc

Index: base/time_win.cc
diff --git a/base/time_win.cc b/base/time_win.cc
index 71c914da29dabe75003d9e83172269d3ac72a717..0e1c67ed65143366361d464f1713fa20a2b67415 100644
--- a/base/time_win.cc
+++ b/base/time_win.cc
@@ -371,6 +371,11 @@ class HighResNowSingleton {
     return abs(static_cast<long>((UnreliableNow() - ReliableNow()) - skew_));
   }
 
+  TimeDelta FromQPCValue(LONGLONG qpcValue) {
+    return TimeDelta::FromMicroseconds(
+             static_cast<int64>(qpcValue / ticks_per_microsecond_));

[jar (doing other things), 2012/07/30 21:31:52]

nit: only use an indent of 4 beyond the start of the word "return".  

Note for instance, when you wrap a super long line that you can't align with the
paren, you don't add extra indentation beyond the 4 spaces.  Good example is
given in:

http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml?showone=Functi...

+  }
+
  private:
   HighResNowSingleton()
     : ticks_per_microsecond_(0.0),

[jar (doing other things), 2012/07/30 21:31:52]

nit: colon should be indent 4 characters from the "H"

@@ -389,8 +394,8 @@ class HighResNowSingleton {
     LARGE_INTEGER ticks_per_sec = {0};
     if (!QueryPerformanceFrequency(&ticks_per_sec))
       return;  // Broken, we don't guarantee this function works.
-    ticks_per_microsecond_ = static_cast<float>(ticks_per_sec.QuadPart) /
-      static_cast<float>(Time::kMicrosecondsPerSecond);
+    ticks_per_microsecond_ = static_cast<double>(ticks_per_sec.QuadPart) /
+      static_cast<double>(Time::kMicrosecondsPerSecond);
 
     skew_ = UnreliableNow() - ReliableNow();
   }
@@ -409,7 +414,7 @@ class HighResNowSingleton {
 
   // Cached clock frequency -> microseconds. This assumes that the clock
   // frequency is faster than one microsecond (which is 1MHz, should be OK).
-  float ticks_per_microsecond_;  // 0 indicates QPF failed and we're broken.
+  double ticks_per_microsecond_;  // 0 indicates QPF failed and we're broken.
   int64 skew_;  // Skew between lo-res and hi-res clocks (for debugging).
 
   friend struct DefaultSingletonTraits<HighResNowSingleton>;
@@ -446,6 +451,19 @@ int64 TimeTicks::GetQPCDriftMicroseconds() {
 }
 
 // static
+TimeTicks TimeTicks::FromQPCValue(LONGLONG qpcValue) {
+    return TimeTicks() +
+           HighResNowSingleton::GetInstance()->FromQPCValue(qpcValue);

[jar (doing other things), 2012/07/30 21:31:52]

nit: 4 character indent off start of "return"

+}
+
+// static
 bool TimeTicks::IsHighResClockWorking() {
   return HighResNowSingleton::GetInstance()->IsUsingHighResClock();
 }
+
+// TimeDelta ------------------------------------------------------------------
+
+// static
+TimeDelta TimeDelta::FromQPCValue(LONGLONG qpcValue) {
+    return HighResNowSingleton::GetInstance()->FromQPCValue(qpcValue);
+}