Issue #1507 - Remove nsRefreshDriver's use of high res system timers.

Since we are using vsync for timing anyway in the layout refresh driver,
there is no need to bump the system timer resolution down to 1 ms.

This resolves #1507.

layout/base/nsRefreshDriver.h

@@ -450,7 +450,6 @@ private:
   bool mNeedToRecomputeVisibility;
   bool mTestControllingRefreshes;
   bool mViewManagerFlushIsPending;
-  bool mRequestedHighPrecision;
   bool mInRefresh;
 
   // True if the refresh driver is suspended waiting for transaction
@@ -502,10 +501,6 @@ private:
 
   friend class mozilla::RefreshDriverTimer;
 
-  // turn on or turn off high precision based on various factors
-  void ConfigureHighPrecision();
-  void SetHighPrecisionTimersEnabled(bool aEnable);
-
   static void Shutdown();
 
   // `true` if we are currently in jank-critical mode.