Revert of Initialize the now_funciton to the HighResNowWrapper in case High Res is supported

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 27bcd1876da0d414ad14764c96b88d98561da722..5fa899d1f97f69be69d1df65ba854565d7240b53 100644
--- a/base/time/time_win.cc
+++ b/base/time/time_win.cc
@@ -359,24 +359,21 @@
 class HighResNowSingleton {
  public:
   HighResNowSingleton()
-      : ticks_per_second_(0),
-        skew_(0) {
+    : ticks_per_second_(0),
+      skew_(0) {
+    InitializeClock();
 
     base::CPU cpu;
     if (IsBuggyAthlon(cpu))
-      return;
-
-    // Synchronize the QPC clock with GetSystemTimeAsFileTime.
-    LARGE_INTEGER ticks_per_sec = {0};
-    if (!QueryPerformanceFrequency(&ticks_per_sec))
-      return; // QPC is not available.
-    ticks_per_second_ = ticks_per_sec.QuadPart;
-
-    skew_ = UnreliableNow() - ReliableNow();
+      DisableHighResClock();
   }
 
   bool IsUsingHighResClock() {
-    return ticks_per_second_ != 0;
+    return ticks_per_second_ != 0.0;
+  }
+
+  void DisableHighResClock() {
+    ticks_per_second_ = 0.0;
   }
 
   TimeDelta Now() {
@@ -411,6 +408,16 @@
   }
 
  private:
+  // Synchronize the QPC clock with GetSystemTimeAsFileTime.
+  void InitializeClock() {
+    LARGE_INTEGER ticks_per_sec = {0};
+    if (!QueryPerformanceFrequency(&ticks_per_sec))
+      return;  // Broken, we don't guarantee this function works.
+    ticks_per_second_ = ticks_per_sec.QuadPart;
+
+    skew_ = UnreliableNow() - ReliableNow();
+  }
+
   // Get the number of microseconds since boot in an unreliable fashion.
   int64 UnreliableNow() {
     LARGE_INTEGER now;
@@ -439,6 +446,7 @@
 }
 
 typedef TimeDelta (*NowFunction)(void);
+NowFunction now_function = RolloverProtectedNow;
 
 bool CPUReliablySupportsHighResTime() {
   base::CPU cpu;
@@ -451,14 +459,6 @@
 
   return true;
 }
-
-NowFunction GetNowFunction() {
-  if (!CPUReliablySupportsHighResTime())
-    return RolloverProtectedNow;
-  return HighResNowWrapper;
-}
-
-NowFunction now_function = GetNowFunction();
 
 }  // namespace
 
@@ -474,6 +474,16 @@
 }
 
 // static
+bool TimeTicks::SetNowIsHighResNowIfSupported() {
+  if (!CPUReliablySupportsHighResTime()) {
+    return false;
+  }
+
+  now_function = HighResNowWrapper;
+  return true;
+}
+
+// static
 TimeTicks TimeTicks::Now() {
   return TimeTicks() + now_function();
 }